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Thread: "How do planes follow the curvature of Earth's atmosphe

  1. #1 "How do planes follow the curvature of Earth's atmosphe 
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    "How does an airplane mysteriously follow the curvature of the Earth's atmosphere?"

    You read it correctly. Yes!!!! How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.


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  3. #2 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by newcastle
    "How does an airplane mysteriously follow the curvature of the Earth's atmosphere?"

    You read it correctly. Yes!!!! How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.
    Gravity.


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  4. #3 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by newcastle
    "How does an airplane mysteriously follow the curvature of the Earth's atmosphere?"

    You read it correctly. Yes!!!! How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.
    ---------------------------------------------
    Gravity.
    Now that's funny, man developed the jet engine to defy gravity, provided of course fuel doesn't run-out because after that, well, man and machine meet the ground courtesy of Gravity.

    Nice try.
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  5. #4  
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    I think of it as a centripetal force idea. An object that is "orbiting" another object has a force applied to it that is always directed toward the center of its circular path and always perpendicular to its velocity at any particular time.


    In the image above this type of idea is expressed using a hockey puck attached to a string where the tension in the string is the centripetal force that pulls the puck toward the center. If you want to imagine the larger Earth scale, just replace the tension of the string with the gravity of Earth.

    This is also the same exact idea that satalites use to effortlessly stay in orbit. The only force needed is gravity in the case of the satalites.
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  6. #5  
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    Man alive everybodies is asleep, dang it when you guy's wake this world is gonna rock.
    Quote Originally Posted by Demen Tolden
    I think of it as a centripetal force idea. An object that is "orbiting" another object has a force applied to it that is always directed toward the center of its circular path and always perpendicular to its velocity at any particular time.
    I'm not to sure exactly what your saying, but if I were to guess the logic behind what you're trying to say, then, that would be like saying when the plane cruses at 30,000 ft on a flat surface below and encounters mountains of say 3000 ft the plane would automatically elevate to regulate that centripetal force, that doesn't happen if you ever traveled coast to coast.
    Quote Originally Posted by Demen Tolden
    This is also the same exact idea that satalites use to effortlessly stay in orbit. The only force needed is gravity in the case of the satalites.
    There is no orbit in space, why do you think they call it "the space walk" you can actually walk on the atmosphere. This is the line that hooked a generation to sink lower then previous one.

    "The ISS free-falls as it orbits the Earth. If there were no forces acting on the ISS, it would travel in a straight line away from the Earth. Because the Earth pulls the ISS towards it and is traveling 7900 meters per second (26,000 feet per second) parallel to the Earth's surface, the ISS moves around the Earth in a circle. Astronauts in the ISS appear to be floating, but it is more correct to say they are in "free fall."

    http://ksnn.larc.nasa.gov/webtext.cfm?unit=float

    The Question:

    When you drive your car on your city roads (on the planes) the atmosphere is level to this surface you're driving on, only parallel 300 km up. You know that your car is moving forward because you've got your foot on the gas pedal, but if you take your foot off it your car begins to slow down and finally comes to a stop, so, "how does the ISS or Shuttle who are on the same flat surface plane in regards to the atmosphere be traveling this so-called orbit?"

    The gases that layer up one on top of the other (atmosphere) are held by a force, that force is called gravity, if we on Earth had no gravity our cars would take longer to slow-down because there would be no friction, the air would be the only assistance to that slow-down. So, since the Shuttle sits on these gases held down by that force called gravity it too will slow-down, granted, it will take longer for there is no air to assist in that deceleration. But the question still remains, "how does the Shuttle achieve orbit without propulsion?"

    And because the atmosphere is level and parallel to your everyday rural areas of your neighbor-hood. The Shuttle would be sitting on an exact horizontal plane such as the spaces of your own surroundings, there would be no way for the Shuttle to go forward without propulsion. Think of it in this way, if you lay a ball on the ground will this ball start falling around the round Earth? Not my ball, so, if the same ball is taken directly over-head of that same spot and laid on the atmosphere will that ball start falling around the round Earth and achieve what we've come to believe is orbit?

    Maybe this link will help with a visual, picture the Space-Shuttle sitting at 250 km, now look to ground zero, see how flat the ground is? That's how flat the atmosphere is up there following the flat ground below.

    http://ds9.ssl.berkeley.edu/LWS_GEMS...3/emrad510.jpg
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  7. #6 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by newcastle
    "How does an airplane mysteriously follow the curvature of the Earth's atmosphere?"

    You read it correctly. Yes!!!! How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.
    The plane is probably on auto pilot most of the time, to be honest with you. And that adjusts for altitude. The plane is continuously moving up and down a bit. Between certain pressures, or according to other electronic devices that determine altitude. Sometimes a caption could fly by the planes level indicator. And just hold the plane to a certain levelness. And then every now and then adjust for altitude. There are a lot of ways you can fly a plane successfully.

    The earths surface is moving along at about 1000 miles an hour at the equator. Now if you combined that with the top speed a jet can fly, your plane is really moving. And may experience a slight drop in weight. If that is true a caption could nose down the plane and make use of this slight lack of weight. And increase the speed of the place further still.

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  8. #7  
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    The pilots or autopilot maintain the height from sea level.


    The Russian MIGs and the BlackBird (also the COndor I think) can actually reach space but are not equipped for reentry.
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  9. #8 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by newcastle
    "How does an airplane mysteriously follow the curvature of the Earth's atmosphere?"

    You read it correctly. Yes!!!! How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.
    1. How do you they don't? The curvature of the Earth is so slight that this would ony require an adjustment of less than 1/10 of a degree per every 10 km traveled.

    2. A pilot is constantly adjusting the attitude of the nose of the plane to maintain altitude, due to a number of factors: rising and falling air columns, changing barometric pressure, etc. Even without all these things, it would be very difficult to hold an aircraft' nose at a set attitude with out constant adjustments. These adjustments would completely swamp out any 1/10 of a degree correction per 10 Km. IOW, a pilot could be applying such a correction all the time and not ever be aware of it.

    3. Jet engines do not "defy gravity", they provide thrust so that the wings can generate lift. Lift is generated via the "angle of attack" of the wings. To increase lift and gain altitude you have to increase the angle of attack. To increase the angle of attack you pull back on the yoke. To climb, you have to maintain a constant back pressure on the yoke to keep the angle of attack high. If you release pressure on the stick, the angle of attack will return to its previous value and the nose will drop back to its previous attitude.

    IOW, aerodynamics of the aircraft will cause it to maintain a fixed (excluding the effects mentioned earlier) attitude with respect to the horizon without pilot correction.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  10. #9 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by newcastle
    Quote Originally Posted by DrRocket
    Quote Originally Posted by newcastle
    "How does an airplane mysteriously follow the curvature of the Earth's atmosphere?"

    You read it correctly. Yes!!!! How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.
    ---------------------------------------------
    Gravity.
    Now that's funny, man developed the jet engine to defy gravity, provided of course fuel doesn't run-out because after that, well, man and machine meet the ground courtesy of Gravity.

    Nice try.
    Defying gravity is just a turn of phrase newcastle. Aircraft don't escape gravity. If they did they'd be able to leave Earth orbit entirely. They can't because they aren't able to go fast enough to break free of gravity. Unless ascending or descending, they fly on a path perpendicular to the local centre of gravity.
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  11. #10  
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    Quote Originally Posted by newcastle
    Man alive everybodies is asleep, dang it when you guy's wake this world is gonna rock.
    Quote Originally Posted by Demen Tolden
    I think of it as a centripetal force idea. An object that is "orbiting" another object has a force applied to it that is always directed toward the center of its circular path and always perpendicular to its velocity at any particular time.
    I'm not to sure exactly what your saying, but if I were to guess the logic behind what you're trying to say, then, that would be like saying when the plane cruses at 30,000 ft on a flat surface below and encounters mountains of say 3000 ft the plane would automatically elevate to regulate that centripetal force, that doesn't happen if you ever traveled coast to coast.
    Quote Originally Posted by Demen Tolden
    This is also the same exact idea that satalites use to effortlessly stay in orbit. The only force needed is gravity in the case of the satalites.
    There is no orbit in space, why do you think they call it "the space walk" you can actually walk on the atmosphere. This is the line that hooked a generation to sink lower then previous one.

    "The ISS free-falls as it orbits the Earth. If there were no forces acting on the ISS, it would travel in a straight line away from the Earth. Because the Earth pulls the ISS towards it and is traveling 7900 meters per second (26,000 feet per second) parallel to the Earth's surface, the ISS moves around the Earth in a circle. Astronauts in the ISS appear to be floating, but it is more correct to say they are in "free fall."

    http://ksnn.larc.nasa.gov/webtext.cfm?unit=float

    The Question:

    When you drive your car on your city roads (on the planes) the atmosphere is level to this surface you're driving on, only parallel 300 km up. You know that your car is moving forward because you've got your foot on the gas pedal, but if you take your foot off it your car begins to slow down and finally comes to a stop, so, "how does the ISS or Shuttle who are on the same flat surface plane in regards to the atmosphere be traveling this so-called orbit?"

    The gases that layer up one on top of the other (atmosphere) are held by a force, that force is called gravity, if we on Earth had no gravity our cars would take longer to slow-down because there would be no friction, the air would be the only assistance to that slow-down. So, since the Shuttle sits on these gases held down by that force called gravity it too will slow-down, granted, it will take longer for there is no air to assist in that deceleration. But the question still remains, "how does the Shuttle achieve orbit without propulsion?"

    And because the atmosphere is level and parallel to your everyday rural areas of your neighbor-hood. The Shuttle would be sitting on an exact horizontal plane such as the spaces of your own surroundings, there would be no way for the Shuttle to go forward without propulsion. Think of it in this way, if you lay a ball on the ground will this ball start falling around the round Earth? Not my ball, so, if the same ball is taken directly over-head of that same spot and laid on the atmosphere will that ball start falling around the round Earth and achieve what we've come to believe is orbit?

    Maybe this link will help with a visual, picture the Space-Shuttle sitting at 250 km, now look to ground zero, see how flat the ground is? That's how flat the atmosphere is up there following the flat ground below.

    http://ds9.ssl.berkeley.edu/LWS_GEMS...3/emrad510.jpg
    Science is not your friend Newcastle. Seriously, the above is beyond rubbish. Move to pseudoscience mod?
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  12. #11 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by William McCormick
    The plane is probably on auto pilot most of the time, to be honest with you. And that adjusts for altitude. The plane is continuously moving up and down a bit.
    No brother, I've many times flown and if the airplane would move up and down continuously everyone would throw-up, the wings of the plane once at cruising altitude never move! Although if the Earth was round they would have to be adjusted often.
    Quote Originally Posted by William McCormick
    The earths surface is moving along at about 1000 miles an hour at the equator. Now if you combined that with the top speed a jet can fly, your plane is really moving.
    If what you say is true then the flight back against the rotation of the Earth would take much longer, much, much longer. No brother the Earth doesn't move, the Earth is flat and if you would hover a helicopter steady above the ground for hours the ground would not move from underneath.
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  13. #12  
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    Quote Originally Posted by CoolEJ
    The pilots or autopilot maintain the height from sea level.
    Yes the airspeed indicator and altimeter are located on the nose of the fuselage or on the edge of the wings, the altimeter shows altitude by measuring precisely barometric pressure. Just like a barometer.

    But that doesn't answer the O-P, thank-you come again!!!!
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  14. #13 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by Janus
    1. How do you they don't? The curvature of the Earth is so slight that this would ony require an adjustment of less than 1/10 of a degree per every 10 km traveled.
    Its not slight look at a globe, if your flying from the city of Angels to Australia you'll note that if the pilot doesn't do fancy and continuous adjustments the airplane would be headed straight for Uranus....
    Quote Originally Posted by Janus
    2. A pilot is constantly adjusting the attitude of the nose of the plane to maintain altitude, due to a number of factors: rising and falling air columns, changing barometric pressure, etc.
    Wrong, if you have ever been on a plane the flaps of the wings (aileron) never move not once at cruising level....
    Quote Originally Posted by Janus
    3. Jet engines do not "defy gravity", they provide thrust so that the wings can generate lift.
    No wrong as usual, defying gravity doesn't mean eliminating gravity. So I will define gravity.

    de·fy: dɪˈfaɪ; n. dɪˈfaɪ, ˈdifaɪ/ Pronunciation Key - Show Spelled Pronunciation [v. di-fahy; n. di-fahy, dee-fahy]

    1. to challenge the power of; resist boldly or openly: to defy parental authority.
    2. to offer effective resistance to:
    3. to challenge; to do something deemed impossible:

    Just like the birds of Heaven when they spread their wings and defy the Law (gravity) that maintains the order of the Earth. These birds don't eliminate the Law and can continue to do this until their feathers are plucked.
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  15. #14 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by TheBiologista
    Now that's funny, man developed the jet engine to defy gravity, provided of course fuel doesn't run-out because after that, well, man and machine meet the ground courtesy of Gravity.
    ---------------------------
    Defying gravity is just a turn of phrase newcastle. Aircraft don't escape gravity. If they did they'd be able to leave Earth orbit entirely. They can't because they aren't able to go fast enough to break free of gravity. Unless ascending or descending, they fly on a path perpendicular to the local centre of gravity.
    You have just defined the word defying, thank-you, per your definition is how I have used it in my reply. Now tackle the O-P!!!!
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  16. #15  
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    Quote Originally Posted by TheBiologista
    When you drive your car on your city roads (on the planes) the atmosphere is level to this surface you're driving on, only parallel 300 km up. You know that your car is moving forward because you've got your foot on the gas pedal, but if you take your foot off it your car begins to slow down and finally comes to a stop, so, "how does the ISS or Shuttle who are on the same flat surface plane in regards to the atmosphere be traveling this so-called orbit?"

    The gases that layer up one on top of the other (atmosphere) are held by a force, that force is called gravity, if we on Earth had no gravity our cars would take longer to slow-down because there would be no friction, the air would be the only assistance to that slow-down. So, since the Shuttle sits on these gases held down by that force called gravity it too will slow-down, granted, it will take longer for there is no air to assist in that deceleration. But the question still remains, "how does the Shuttle achieve orbit without propulsion?"

    And because the atmosphere is level and parallel to your everyday rural areas of your neighbor-hood. The Shuttle would be sitting on an exact horizontal plane such as the spaces of your own surroundings, there would be no way for the Shuttle to go forward without propulsion. Think of it in this way, if you lay a ball on the ground will this ball start falling around the round Earth? Not my ball, so, if the same ball is taken directly over-head of that same spot and laid on the atmosphere will that ball start falling around the round Earth and achieve what we've come to believe is orbit?
    ---------------------------------------------------------------
    Science is not your friend Newcastle. Seriously, the above is beyond rubbish. Move to pseudoscience mod?
    When opposing logic is too strong and cannot be disputed the next best thing to keep the light from waking those who sleep in darkness is exactly what you suggested, "get rid of it quick, for we cannot compete with Truth!"
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  17. #16 Re: "How do planes follow the curvature of Earth's atmo 
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    [quote="newcastle"]
    Quote Originally Posted by Janus

    Quote Originally Posted by Janus
    2. A pilot is constantly adjusting the attitude of the nose of the plane to maintain altitude, due to a number of factors: rising and falling air columns, changing barometric pressure, etc.
    Wrong, if you have ever been on a plane the flaps of the wings (aileron) never move not once at cruising level....
    I've not only been on a plane, I've piloted a plane.

    The ailerons are used to control roll not pitch. (and are completely different control surfaces from the flaps.) the control surface that controls pitch is the elevator (typically located on the tail of the aircraft.)
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  18. #17  
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    Quote Originally Posted by newcastle
    There is no orbit in space, why do you think they call it "the space walk" you can actually walk on the atmosphere.
    Why do you think the satellites move? And why do satellites that should stay fixed on a position over the Earth have to be put on the geo-stationary orbit 36000 km above the Earth? These orbits are needed to get a force equilibrium between the Earths gravity and the centrifugal force of the satellite. The net sum of forces is then zero. This is why it feels like zero gravity. In fact, the correct term is microgravity.

    Quote Originally Posted by newcastle
    "how does the ISS or Shuttle who are on the same flat surface plane in regards to the atmosphere be traveling this so-called orbit?"
    ...
    But the question still remains, "how does the Shuttle achieve orbit without propulsion?"
    Look here for a graph showing the changing altitude of the ISS. You see that due to friction with the upper (not absent) atmosphere, the ISS is breaking and consequently losing altitude. It rises again by gaining speed through firing boosters. Mostly it's the rockets of the docked spacecrafts and service modules.

    http://www.space.com/missionlaunches...ssreboost.html
    http://www.space.com/missionlaunches...oost_test.html

    Of course, the shuttle has its own thrusters that are used frequently to keep its altitude.
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  19. #18 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by newcastle
    Quote Originally Posted by William McCormick
    The plane is probably on auto pilot most of the time, to be honest with you. And that adjusts for altitude. The plane is continuously moving up and down a bit.
    No brother, I've many times flown and if the airplane would move up and down continuously everyone would throw-up, the wings of the plane once at cruising altitude never move! Although if the Earth was round they would have to be adjusted often.
    Quote Originally Posted by William McCormick
    The earths surface is moving along at about 1000 miles an hour at the equator. Now if you combined that with the top speed a jet can fly, your plane is really moving.
    If what you say is true then the flight back against the rotation of the Earth would take much longer, much, much longer. No brother the Earth doesn't move, the Earth is flat and if you would hover a helicopter steady above the ground for hours the ground would not move from underneath.

    The tail of the plane moves almost continuously, if on auto pilot. The amount or the degree it moves may be very small. However it moves.

    It is called the elevator and it moves, to cause the plane to head up or down. The ailerons tilt the plane left to right, they are located on the wings, they also move.

    The rudder is also on the tail, and it moves the plane left to right, it does not tilt the plane, it just turns the plane left or right.

    Although you can over a distance make turns with the ailerons as well. Many do use them for turning.

    The flat earth may start to seem real to some, because of all the nonsense from many governments. However the earth is round.


    Sincerely,


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  20. #19 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by Janus
    I've not only been on a plane, I've piloted a plane.

    The ailerons are used to control roll not pitch. (and are completely different control surfaces from the flaps.) the control surface that controls pitch is the elevator (typically located on the tail of the aircraft.)
    True enough, and its hard to see those tail elevators but you can hear the motor (hydraulics) of the elevators, just like you can hear the motors of the aileron and spoilers, oh yes, and flaps too. I have flown on the cheapo seats, no noise, no nose pitch of the aircraft every now and about. The Earth is Flat.
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    Quote Originally Posted by Dishmaster
    1) You see that due to friction with the upper (not absent) atmosphere, the ISS is breaking and consequently losing altitude. It rises again by gaining speed through firing boosters. Mostly it's the rockets of the docked spacecrafts and service modules.

    2) Of course, the shuttle has its own thrusters that are used frequently to keep its altitude.
    1 and 2 are false, I'm very sorry that I must correct you. The tiles on the Shuttle is the give away if you're seeking Truth. These tiles don't heat up on lift-off only on re-entering, because the friction is so incredible that the Shuttle is literally drilling into those gases, and just like a drill bit it will heat up. Upon take-off when the Shuttle thrust through the atmosphere and into outer space, the emptiness of space allows that where ever the Shuttle rests upon something that “something” becomes a support for the Shuttle, in this case, that “something” are the layers of gases pile up one on top of the other known as the atmosphere. At this height and being on the outside into the emptiness this “something” (although gases) act like a soft surface, we are able to walk on the atmosphere ("Why do you think they call it the Space Walk?") so when the Shuttle re-enters it needs rocket engine power to drill through this support and the tiles to cool the heat generated.
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  22. #21 Re: "How do planes follow the curvature of Earth's atmo 
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    Quote Originally Posted by William McCormick
    ANSWER THIS QUESTION: If what you say is true, "then the flight back against the rotation of the Earth would take much longer, much, much longer?" Earth doesn't move, the Earth is flat and if you would hover a helicopter steady above the ground for hours the ground would not move from underneath.
    ----------------------------------
    The tail of the plane moves almost continuously, if on auto pilot. The amount or the degree it moves may be very small. However it moves.

    It is called the elevator and it moves, to cause the plane to head up or down. The ailerons tilt the plane left to right, they are located on the wings, they also move.

    The rudder is also on the tail, and it moves the plane left to right, it does not tilt the plane, it just turns the plane left or right.

    Although you can over a distance make turns with the ailerons as well. Many do use them for turning.

    The flat earth may start to seem real to some, because of all the nonsense from many governments. However the earth is round.
    Your a good guy McCormick, but the Earth if Flat.
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  23. #22  
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    Quote Originally Posted by newcastle
    Quote Originally Posted by TheBiologista
    Science is not your friend Newcastle. Seriously, the above is beyond rubbish. Move to pseudoscience mod?
    When opposing logic is too strong and cannot be disputed the next best thing to keep the light from waking those who sleep in darkness is exactly what you suggested, "get rid of it quick, for we cannot compete with Truth!"
    I'm not asking for it to be gotten rid of, but to be moved to an appropriate location. "Pseudoscience" will have to do, since there's no forum titled "Loony Bin".
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  24. #23  
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    Quote Originally Posted by TheBiologista

    When opposing logic is too strong and cannot be disputed the next best thing to keep the light from waking those who sleep in darkness is exactly what you suggested, "get rid of it quick, for we cannot compete with Truth!"
    ---------------------------
    I'm not asking for it to be gotten rid of, but to be moved to an appropriate location. "Pseudoscience" will have to do, since there's no forum titled "Loony Bin".
    But you can't mount a sound agrument against the O-P and it is that embarrassment that has become the willing to have it removed elsewhere, out of sight, out of mind.
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    I find that math is usually a pretty aggreable method to problem solving, so lets draw a free body diagram and start from there.



    Are these forces disputed at all?

    If not, then we can start plugging in forumlas.
    First of all, by Newton's second law:

    where F is the indicated force, mass is the mass of the plane, and a is the acceleration of the plane in the direction of the indicated force. For example, when considering the gravitational force, the acceleration of this gravitational force is in the -y direction. When considering the drag, the acceleration of this force is in the +x direction.
    Next:
    The acceleration due to gravity is about 9.8 m/s<sup>2</sup>. This can be tested by measuring distance that an object falls if you measure it in periodic intervals if you like. Of course the pull of gravity may decrease the farther we get away from earth so in order to do a satisfactory test of gravity on a plane, we may have to do some skydiving.
    But if we are ok with being a bit inaccurate we could use 9.8 m/<sup>2</sup>. This means that our gravitational force is equal to:

    I've also learned that the equation of the force of the drag is equal to:

    though I actually am not quite sure at the moment how to derive this equation. D is the drag, C is an experiementally determined drag coeficient, p is the density of the fluid or gas which our solid object is passing through, A is the effective cross-sectional area, and v is the velocity of our object in reference to our flowing liquid or gas.
    I am not too sure about how to determine thrust and lift though.
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    Man, you really are something else, aren't you? :? You just come back with ridiculous "first hand accounts" where you supposedly have witnessed the opposite of the point made. Liar!

    Another thing, air pressure varies with altitude. With the plane on a certain thrust level, only a certain amount of lift can be expected from any wing configuration. So, on average (assuming a very calm atmosphere), the plane would enter less dense air as its altitude increases, the amount of lift would be reduced and the plane would automatically readjust to an altitude where gravity and lift is in equilibrium.

    But of course you will say that the air pressure is equal throughout the atmosphere, effectively disregarding the experience of all the pilots that have ever flown and all pressure measurements ever taken! Amazing….
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Listen dudes, don't pay attention to these University drop-outs.

    At point (A) the airplane reaches cruising altitude and pilot engages trim tabs, the ground below is a given 34,000 ft, upon reaching point (B) 500 miles later the ground below curved underneath around the so-called round Earth and gained altitude. Now the airplane has to reach point (E), therefore altitude adjustment must be implemented or air routes are compromised.

    At point (A) were the trim tabs adjusted, but when the airplane reaches point (B) the curvature of the round Earth declined and new adjustment must be implemented because the airplane is no longer at point (A).

    Riddle me this!!!!

    Those pilots would have to make adjustments, and because its hard to see those tail elevators, but you can hear the motor (hydraulics) of the elevators, just like you can hear the motors of the aileron and spoilers, oh yes, and flaps too. Either way, which ever way you choose to represent your point whether the aircraft follows the surface of the Earth or the pressure of the air both curve on a round Earth and because the airplane is flying perpendicular from point (A) being of surface or of air, upon reaching point (B) adjustments will have to be made using Hydraulic elevators - noise - nose pitch!!!!! But the ride of the airplane is always leveled once in cruising altitude, so, this proves to all who have flown that the Earth is Flat, and nobody here on this forum, or on any other monkey forum will prove otherwise....
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    Damn, you beat me Demen! I thought he'd say that the atmosphere is invariant in density, but instead he just ignored the whole point by us both!
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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  29. #28  
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    Quote Originally Posted by newcastle
    But you can't mount a sound agrument against the O-P
    I think you'll find that several of the others have. They've already explained far better than I could, in fact.

    Quote Originally Posted by newcastle
    ...and it is that embarrassment that has become the willing to have it removed elsewhere, out of sight, out of mind.
    There are only so many ways to explain to you that the world is roughly a sphere. Ultimately, it is only your own unwillingness to go see for yourself that holds you back. You'll continue to say white is black via a wide variety of extremely dim-witted "challenges" irrespective of what anyone says, thus your argument has no place on a science forum. You've made your mind up without testing it. That's not science, it's faith.

    Quote Originally Posted by newcastle
    Listen dudes, don't pay attention to these University drop-outs.
    More assumption. I have a first class honours degree and am currently writing up my doctorate. These qualifications are utterly irrelevant however, since your argument displays a sub high school grasp of basic physics and no grasp at all of the scientific method. The only qualification needed to defeat your logic is a pair of binoculars and an uninterrupted view of the horizon.
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    Quote Originally Posted by newcastle
    Quote Originally Posted by CoolEJ
    The pilots or autopilot maintain the height from sea level.
    Yes the airspeed indicator and altimeter are located on the nose of the fuselage or on the edge of the wings, the altimeter shows altitude by measuring precisely barometric pressure. Just like a barometer.

    But that doesn't answer the O-P, thank-you come again!!!!

    It does answer if you open your mind.

    The pilot or autopilot adjusts the height of the flight. You don't feel it because the adjustment is not that noticeable. Otherwise, drawing a straight line on a curved surface would mean exiting the atmosphere or stalling (due to lack of gas).

    Please do not argue that the earth is flat. If you intend to, go back to the time of Columbus and Magellan. Or maybe take peak at the Hubble's Scope so you can check it first hand.
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    I'd like to add to what I said just in case you still do not get it.

    So what if it adjusts the height?

    If you adjust the height , which is relative to the sea surface, you will be following the curvature of the earth.
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    Quote Originally Posted by TheBiologista
    There are only so many ways to explain to you that the world is roughly a sphere.
    Yeah, the only sphere in the Universe with Flat arcs, lol, "who do you think your foolin?"

    Everywhere you go the round Earth its Flat!!!! Where are the curves of the Earth? Where's the proof? We can see the FLATNESS of the round Earth, but what's funny is that we CAN"T see the ROUNDNESS of the round Earth, lol, man alive drink your coffee no milk & sugar dammit WAKE-UP!!!!!!!
    Quote Originally Posted by TheBiologista
    More assumption. I have a first class honours degree and am currently writing up my doctorate. These qualifications are utterly irrelevant however, since your argument displays a sub high school grasp of basic physics and no grasp at all of the scientific method. The only qualification needed to defeat your logic is a pair of binoculars and an uninterrupted view of the horizon.
    You couldn't stand eye to eye with me on any subject, not until you accept and praise the Blesseth Holy Enoch and the LORD of Spirits.
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    Quote Originally Posted by CoolEJ
    It does answer if you open your mind.
    The problem with an open mind is that the brain can fall off.
    Quote Originally Posted by CoolEJ
    The pilot or autopilot adjusts the height of the flight. You don't feel it because the adjustment is not that noticeable. Otherwise, drawing a straight line on a curved surface would mean exiting the atmosphere or stalling (due to lack of gas).
    You must be TROLLING, no-one, but no-one can possibly be this obtuse. How can you point your trim elevators down in projection of point (B) while your flight coordinates are at point (A) and still keep the nose of the aircraft up? ITS NOT POSSIBLE!!!!

    The said airplane sets its trim elevators from point (A) for point (A) and flying the so-called round Earth's surface would curve in around the Earth that upon reaching point (B) the plane would be above chartered air routes and at risk so that pilot intervention would require to descend or drop altitude. The pilot will always have to intervene to adjust the altitude every now and then, but they don't. And anyone who's flown will testify to that fact that when at cruising altitude the ride is smooth and steady. No noise coming from the hydraulic elevators nor that nauseating feeling in your gut when the aircraft drops altitude on the downward pitch of the aircraft's nose, the Earth is Flat.... END OF STORY....
    Quote Originally Posted by CoolEJ
    Please do not argue that the earth is flat. If you intend to, go back to the time of Columbus and Magellan. Or maybe take peak at the Hubble's Scope so you can check it first hand.
    Yes, the days of exploration. Look to the old maps of the first explores who sailed. You will note something that is no longer printed on the new ones. All the old maps have the North Ice dispersed equally along the length of that map and also the South Ice. If the south pole was truly Antarctica it would not have appeared so vast and wide as those who sailed during the days of exploration, it would have been drawn like the rest of the continents. But those sailors kept their compass pointing at the center of the Earth (magnetic abyss) and traveled to the edge as far as possible that the ocean ice permitted, and all they saw was ice forming close to them as they traveled in a circle around the magnetic center (abyss) on the flat Earth they documented that Ice on their maps.
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    Is there some rule here in the forums to deal with this kind of posts?
    I think this guy is trolling and messing around.
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  35. #34  
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    Quote Originally Posted by newcastle
    You couldn't stand eye to eye with me on any subject, not until you accept and praise the Blesseth Holy Enoch and the LORD of Spirits.
    Fairy tales are for children.
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  36. #35  
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    Quote Originally Posted by CoolEJ
    Is there some rule here in the forums to deal with this kind of posts?
    I think this guy is trolling and messing around.
    There should be.

    Trolls like you should not have to post replies on my thread.
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    [quote="TheBiologista"]
    Quote Originally Posted by newcastle
    You couldn't stand eye to eye with me on any subject, not until you accept and praise the Blesseth Holy Enoch and the LORD of Spirits.
    --------------------------------------------------
    Fairy tales are for children.
    And soon child you'll put your science books right next to the Pinocchio and Alice in Wonderland shelf.
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  38. #37  
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    Quote Originally Posted by CoolEJ
    Is there some rule here in the forums to deal with this kind of posts?
    I think this guy is trolling and messing around.
    Difficult to tell whether he is trolling or merely mentally deficient. I favour the latter explanation based upon the high level of commitment needed to troll continuously. (I've tried trolling as an idiot and it is really difficult to maintain for any length of time. :wink: )

    As for Newcastle, I usually let his threads stay in proper forums initially, allowing other posters to debunk his nonsense. When he gets truly silly - as I see he has now - I move it to pseudoscience. Look on it as a form of inexpensive entertainment.
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  39. #38  
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    Quote Originally Posted by Ophiolite
    Is there some rule here in the forums to deal with this kind of posts?
    I think this guy is trolling and messing around.
    ---------------------
    Difficult to tell whether he is trolling or merely mentally deficient. I favour the latter explanation based upon the high level of commitment needed to troll continuously. (I've tried trolling as an idiot and it is really difficult to maintain for any length of time. :wink: )

    As for Newcastle, I usually let his threads stay in proper forums initially, allowing other posters to debunk his nonsense. When he gets truly silly - as I see he has now - I move it to pseudoscience. Look on it as a form of inexpensive entertainment.
    Ah Ophiolite.


    I have always appreciated and been entertained by Troll replies such as yours.


    Thank-you for your expertise on this the highest trollology of replies - Come Again!
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  40. #39  
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    [quote="newcastle"]
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by newcastle
    You couldn't stand eye to eye with me on any subject, not until you accept and praise the Blesseth Holy Enoch and the LORD of Spirits.
    --------------------------------------------------
    Fairy tales are for children.
    And soon child you'll put your science books right next to the Pinocchio and Alice in Wonderland shelf.
    Why would I dedicate an entire shelf to Pinocchio and Alice In Wonderland?

    I'm curious Newcastle, what faith do you follow? I assumed at first some branch of Christianity, but now I wonder if you are some manner of Jew? It's hard to judge from your occasional scripture-esque outbursts.
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  41. #40  
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    Quote Originally Posted by newcastle
    Ah Ophiolite.
    I have always appreciated and been entertained by Troll replies such as yours.
    Thank-you for your expertise on this the highest trollology of replies - Come Again!
    Your reply was a blunder. You have demonstrated that you are trolling. The survival rate of your future posts is likely to be low. Your own duration on the forum is likely limited. Tread very carefully.
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  42. #41  
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    Simple answer to the OP: Air pressure drops the further you physically get from the core of the Earth.

    Also: Gravity would begin pulling on you from a slightly rearward angle if you didn't follow the curvature of the Earth.


    The combination of getting pushed on from these two directions:

    1)

    __ (The force applied from behind)

    and

    2)

    / (The force applied by gravity)


    causes the plane to change its orientation.

    The __ force can be interpreted as a combination of a / and \ force, and the two / forces being of opposite direction, they cancel each other, sort of, and only the angular force \ is still acting on the plane, which resists being pushed anywhere that isn't "forward" from the perspective of its wings, so it re-aligns to be facing the way it's getting pushed.

    It's not quite that simple, but the fully complicated version reads pretty similar.
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    Is this the answer you are looking for? The plane doesn't follow the curvature because the earth is flat?
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  44. #43  
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    Err... This thread is 6 years old and in the Pseudoscience section. Such necromancy is usually frowned upon.
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    Is there an expiration date on a topic? If I am not supposed to make comments on threads then why don't they remove the threads? Are you the comment police? Why don't you tell me where I am supposed to comment and what to say. That's ok I am leaving this site anyway. The minute I got on I was attacked. I don't need this.
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  46. #45  
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    Quote Originally Posted by newcastle View Post
    How does the airplane never fly above its cruising altitude as the curvature of the Earth's surface quickly declines beneath the airplane? This should increase the altitude of the level the airplane is flying having the pilots intervene periodically to descend the nose of the aircraft back to cruising altitude.
    No, the plane does that all by itself. Left to its own devices, a properly trimmed aircraft will maintain a certain altitude as determined by the air pressure/density at that altitude. Since the atmosphere follows the curvature of the earth, so does the airplane. A pilot would have to actively increase pitch/power to keep flying in a "straight line", and at some point his aircraft would either run out of power or lift and he would descend back to a circular path.
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  47. #46  
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    Quote Originally Posted by blissweaver View Post
    Is there an expiration date on a topic? If I am not supposed to make comments on threads then why don't they remove the threads? Are you the comment police? Why don't you tell me where I am supposed to comment and what to say. That's ok I am leaving this site anyway. The minute I got on I was attacked. I don't need this.
    That wasn't an attack. Thread necromancy is annoying though. Plus, many times half the people that participated in the original thread aren't active members any more and therefore cannot respond to your comments.

    That said, drop the attitude or you're going to get yourself banned pretty quickly anyway. You may notice that I'm not a moderator, so take this as a friendly warning rather than a threat.
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  48. #47  
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    Quote Originally Posted by blissweaver View Post
    Is there an expiration date on a topic? If I am not supposed to make comments on threads then why don't they remove the threads? Are you the comment police? Why don't you tell me where I am supposed to comment and what to say. That's ok I am leaving this site anyway. The minute I got on I was attacked. I don't need this.
    Nor do we need idiotic remarks such as : "The plane doesn't follow the curvature because the earth is flat?"
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  49. #48  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by blissweaver View Post
    Is there an expiration date on a topic? If I am not supposed to make comments on threads then why don't they remove the threads? Are you the comment police? Why don't you tell me where I am supposed to comment and what to say. That's ok I am leaving this site anyway. The minute I got on I was attacked. I don't need this.
    Nor do we need idiotic remarks such as : "The plane doesn't follow the curvature because the earth is flat?"
    It appeared to me that blissweaver had accurately determined what the troll/idiot poster Newcastle was trying to prove. i.e. that he (Newcastle) believed, or purported to believe, the Earth to be flat. Therefore his remark was both discerning and relevant.

    It was, however, not timely and in that respect Magimaster's advice (not an attack) was welcome.
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  50. #49  
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    Quote Originally Posted by John Galt View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by blissweaver View Post
    Is there an expiration date on a topic? If I am not supposed to make comments on threads then why don't they remove the threads? Are you the comment police? Why don't you tell me where I am supposed to comment and what to say. That's ok I am leaving this site anyway. The minute I got on I was attacked. I don't need this.
    Nor do we need idiotic remarks such as : "The plane doesn't follow the curvature because the earth is flat?"
    It appeared to me that blissweaver had accurately determined what the troll/idiot poster Newcastle was trying to prove. i.e. that he (Newcastle) believed, or purported to believe, the Earth to be flat. Therefore his remark was both discerning and relevant.

    It was, however, not timely and in that respect Magimaster's advice (not an attack) was welcome.
    Thanks John I had missed that sublety and hereby extend an apology to blissweaver for accusing him of posting silly nonsense.
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  51. #50  
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    For possible general interest, and in the unlikely event that the OP writer is still watching this thread;

    Aircraft maintain their altitude by reference to atmospheric pressure. We have two instruments that help us do this, an altimeter and a vertical speed indicator. The altimeter measures the atmospheric pressure outside the aircraft, and the cockpit indicator is calibrated to read thousands of feet, based on a standard pressure (above a certain height). The VSI shows short term changes in pressure, and therefore indicates whether we are climbing or descending, (and will give an indication before the altimeter responds). By keeping the Altimeter to the altitude we have been cleared to and keeping the VSI at zero, we will stay at a particular level. The autopilot will do the same thing.

    As others have said, the flight controls are constantly moving to maintain the correct attitude, although all aircraft have a certain amount of intrinsic stability owing to their design - for example wing dihedral self corrects some roll. Control surface movements in the cruise may be very small, or out of sight in the case of the elevators - which adjust pitch. Above a certain speed some control surfaces are often automatically deactivated. For example the outboard ailerons, since the effect at speed of the inboard ones will be sufficient, and they will apply less bending force to the wings than the outboard ones.

    There is a refinement in that most modern aircraft autopilots will allow small vertical altitude deviations to occur to control the speed, rather than accelerating and decelerating the engines to maintain the required aircraft speed. This 'soft altitude hold'' mode saves fuel.

    Finally, if the OP writer went to the seaside and looked at the sea surface on the horizon, s/he would see the curvature of the ocean. Since water always finds its own level - and cannot vary in height as the land does - the earth must be curved. If you like, take a straight edge a meter long, and line it up to the sea horizon. You will see the curvature then.

    OB
    Last edited by One beer; May 1st, 2014 at 08:05 AM.
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    Hi all. I like reading threads like this - they are entertaining, if nothing else. One thing I've always wondered ..

    Back some posts a while, the OP (?) mentioned a hovering helicopter. Say it was on the equator. The earth DOESN'T rush away from it at 1,000 mph ? Why ? The answer is, I believe, it is carried along by the air pressure, atmoshere, etc, but surely, after a while - let's say it hovered for a day, a difference should be noticable ?

    PS - I joined just to ask this question - it has vexed me for a long time. Though this looks like a great site and I hope to stay involved.
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  53. #52  
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    The only way to define a "hover" is "staying still relative to the ground" so it's a bit circular to wonder why a hovering helicopter stays put. Helicopters do a lot of work just to stay above a certain point. (I do understand the question. I just wanted to point out that it's not a simple thing to answer.)
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    The helicopter might drift from the spot above the earth where it started hovering if the pilot made no corrections, but it will always be under the influence of the air and the air currents (winds), and the air in the atmosphere is rotating with the earth. The strongest jet-streams are about 150 knots, (172 MPH), so even those would not make a huge difference, (and helicopters don't fly high enough to meet jet-streams).

    Only if the helicopter was high enough to be beyond the atmosphere would it be able to drift free, in which case the earth would turn below it while it stayed in the same place in space* - but of course then it would be in orbit! (Obviously a helicopter needs air to make it's blades provide lift, so this could never actually happen.)


    *A geostationary orbit is one at a unique distance from earth - about 36,000km from memory - that allows satellites to orbit the earth but stay above the same point on the ground. This orbit is where all the communications satellites are, so that we don't have to track them with our receiving dishes, which can remain fixed once pointed correctly.

    OB
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    Hello Magicmaster and One beer. Thank you for the replies and pleased to meet you.

    No, I don't believe the earth is flat. These are merely interesting thought paths, which I occasionally tease my kids with, and which sometimes, throw up further interesting questions. Such as ..

    At the equator, earth spins at 1,670 kph, so that's 460 meters per sec, right ?
    My 13 year old asked me - 'When I jump high (he can jump very high) and land in 2 seconds, why aren't I a kilometre away' ?Obvious answer, 'you already have the earths momentum, air pressure', etc.

    Then my 21 year old comes up with this;

    'OK, take a large vacuum chamber - say 60 metres deep. Suspend a heavy lead ball in it, from centre of top to centre of floor, using a very fine line - minimum friction, etc. Reduce it to zero air pressure - total vacuum.

    Now the only forces acting on it are gravity and it's initial momentum.

    It is intuitive and almost common sense to suppose that at some point, it will move off the perpendicular. After all, it is being dragged along at 460 metres every second (at equator).

    Question is, does it ? And has such an experiment or similar, being done ?

    And with the same chamber, drop same ball 60 metres. Does it land slightly off centre ? After all, total vacuum, no air resistance .. and no further maintaining of earths momentum while falling ..

    One would think in both cases, it should be slightly off centre, given that the earth is rushing along at a kilometre every 2 seconds, or so.

    Cheers !

    edit, corrected last line
    Last edited by marcbo; May 18th, 2014 at 09:27 PM. Reason: correction
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    I think what you're referring to is called the Coriolis force. (You'll have to look up the details though. I'm not much of a physicist.)
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    Quote Originally Posted by marcbo View Post
    Hello Magicmaster and One beer. Thank you for the replies and pleased to meet you.

    No, I don't believe the earth is flat. These are merely interesting thought paths, which I occasionally tease my kids with, and which sometimes, throw up further interesting questions. Such as ..

    At the equator, earth spins at 1,670 kph, so that's 460 meters per sec, right ?
    My 13 year old asked me - 'When I jump high (he can jump very high) and land in 2 seconds, why aren't I a kilometre away' ?Obvious answer, 'you already have the earths momentum, air pressure', etc.

    Then my 21 year old comes up with this;

    'OK, take a large vacuum chamber - say 60 metres deep. Suspend a heavy lead ball in it, from centre of top to centre of floor, using a very fine line - minimum friction, etc. Reduce it to zero air pressure - total vacuum.

    Now the only forces acting on it are gravity and it's initial momentum.

    It is intuitive and almost common sense to suppose that at some point, it will move off the perpendicular. After all, it is being dragged along at 460 metres every second (at equator).

    Question is, does it ? And has such an experiment or similar, being done ?

    And with the same chamber, drop same ball 60 metres. Does it land slightly off centre ? After all, total vacuum, no air resistance .. and no further maintaining of earths momentum while falling ..

    One would think in both cases, it should be slightly off centre, given that the earth is rushing along at a kilometre every 2 seconds, or so.

    Cheers !

    edit, corrected last line
    I don't think you would expect to see any effect in the first case (static mass on a line). It is not being dragged along. The line suspending it will pass directly through the centre of the Earth. It is true that the tangential speed of the top support will be slightly greater than that of the suspended mass, but the line will be just like the spoke of a bicycle wheel, or like a tall pole stuck vertically into the ground.

    However in the second case, as there is movement from a larger radius from the centre of the Earth to a slghtly smaller one, then indeed I think I would expect the mass to be seen as moving slightly forward, in the direction of rotation of the Earth, as it falls, due to its tangential speed being slightly greater at higher altitude than that necessary to keep it moving at the same rotational speed at the lower altitude.

    But I agree, it's a slightly tricky couple of scenarios.
    Last edited by exchemist; May 19th, 2014 at 04:48 AM. Reason: word corrected
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    Quote Originally Posted by marcbo View Post
    Then my 21 year old comes up with this;

    'OK, take a large vacuum chamber - say 60 metres deep. Suspend a heavy lead ball in it, from centre of top to centre of floor, using a very fine line - minimum friction, etc. Reduce it to zero air pressure - total vacuum.

    Now the only forces acting on it are gravity and it's initial momentum.

    It is intuitive and almost common sense to suppose that at some point, it will move off the perpendicular. After all, it is being dragged along at 460 metres every second (at equator).

    Question is, does it ? And has such an experiment or similar, being done ?
    Actually, yes: http://blogs.mtu.edu/physics/files/2...lingBodies.pdf

    If you drop an item down a mineshaft it will hit the east wall, because the walls move slower the deeper you go. It's a good argument against Flat Earth Theory.

    That pdf is a transcription from McNair in 1906 but I know experiments have been done by students in modern times. Google gives me 11 million hits so no help there.
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    Quote Originally Posted by Unununium View Post
    Actually, yes: http://blogs.mtu.edu/physics/files/2...lingBodies.pdf

    If you drop an item down a mineshaft it will hit the east wall, because the walls move slower the deeper you go.
    They didn't say how they calculated the ~4 foot eastward drift from the top to the bottom of the mine shaft, so I calculated it myself.
    The speed of the earth's surface is 2*Pi*R/24 miles per hour where R is the earth's radius in miles.
    The speed 1 mile deep is 2*Pi*(R-1)/24, so the difference in speed is
    2*Pi*((R-(R-1))/24 = 2*Pi/24= .26 mph
    Converting to feet per second we get .26mph*(88 fps/60 mph) = .38 fps
    If it falls for 16 seconds, then you would have .38*16 = 6.14 ft
    But they were in Michigan, latitude about 44 degrees (cos 44degrees= .72) so the ball is not falling in a direct line to the earth's axis, so that's 6.14*.72 = 4.4 feet. It wasn't quite a mile deep, so, their 4 foot estimate seems about right.
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    Hi all, and thank you for the replies.

    I will try to reduce the uncertainties I still have, to very simple terms - more for my benefit than any others, and please keep in mind, I am no scientist or mathematician.

    A while back, my wife dangled an ornament from the rear vision mirror inside my car .. as wives do. It is on a thin chain with a relatively heavy metal and glass bauble thingy on the end - it drops about 35cm from the mirror, and when the car is at rest on a horizontal surface (such as in my garage) I notice that the bauble comes to rest directly above the ’P’ (Park) letter of my gear shift slot.

    OK, when I’m driving around town, it of course, gyrates wildly here and there, and not much can be deduced from that.

    BUT, I got thinking about this a while back, in relation to the queries I’ve made in my earlier post here, and I thought I would try an experiment.

    On many occasions, I have to travel a long distance of a 500 km round trip. On such a trip, I look for a location on the motorway, where the road is dead flat and straight in front of me as far as they eye can see, and yes, there are many such locations.

    On those occasions, I observe the bauble thingy. Travelling in a perfectly straight line, at 110 kph, on what is, to the limits of my perception, a perfectly even road surface, the bauble is no longer directly over the ‘P’. It has drifted (is that the right word ?) about one centimetre towards the rear of the car, in the opposite direction of the cars travel.

    I get curious about this. I close all the windows, shut down the air conditioning, and ask the 13 year old to move it back over the ‘P’ by gently pushing forward whilst trying to avoid any other lateral force. He loves this sort of thing .. And does it perfectly.

    I tell him to remove his finger downwards in a moderate motion - not with a flick, so as avoid any turbulence, etc. This too he does. And, the moment his finger no longer touches the bauble, it ‘drifts’ again, towards the rear of the car - by about a centimetre.

    So what’s going on here ? Why does it do this ?

    I want to develop my enquiry concerning issues in my initial post in this thread, but firstly, I would appreciate some replies to this. Thanks.

    edit - corrected 2nd line
    Last edited by marcbo; May 19th, 2014 at 09:45 PM. Reason: corrected 2nd line
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    Quote Originally Posted by marcbo View Post
    Hi all, and thank you for the replies.

    I will try to reduce the uncertainties I still have, to very simple terms - more for my benefit than any others, and please keep in mind, I am no scientist or mathematician.

    A while back, my wife dangled an ornament from the rear vision mirror inside my car .. as wives do. It is on a thin chain with a relatively heavy metal and glass bauble thingy on the end - it drops about 35cm from the mirror, and when the car is at rest on a horizontal surface (such as in my garage) I notice that the bauble comes to rest directly above the ’P’ (Park) letter of my gear shift slot.

    OK, when I’m driving around town, it of course, gyrates wildly here and there, and not much can be deduced from that.

    BUT, I got thinking about this a while back, in relation to the queries I’ve made in my earlier post here, and I thought I would try an experiment.

    On many occasions, I have to travel a long distance of a 500 km round trip. On such a trip, I look for a location on the motorway, where the road is dead flat and straight in front of me as far as they eye can see, and yes, there are many such locations.

    On those occasions, I observe the bauble thingy. Travelling in a perfectly straight line, at 110 kph, on what is, to the limits of my perception, a perfectly even road surface, the bauble is no longer directly over the ‘P’. It has drifted (is that the right word ?) about one centimetre towards the rear of the car, in the opposite direction of the cars travel.

    I get curious about this. I close all the windows, shut down the air conditioning, and ask the 13 year old to move it back over the ‘P’ by gently pushing forward whilst trying to avoid any other lateral force. He loves this sort of thing .. And does it perfectly.

    I tell him to remove his finger downwards in a moderate motion - not with a flick, so as avoid any turbulence, etc. This too he does. And, the moment his finger no longer touches the bauble, it ‘drifts’ again, towards the rear of the car - by about a centimetre.

    So what’s going on here ? Why does it do this ?

    I want to develop my enquiry concerning issues in my initial post in this thread, but firstly, I would appreciate some replies to this. Thanks.

    edit - corrected 2nd line
    This is just a guess. As you are driving forward the car has to overcome rolling friction and air resistance. This is done through the torque supplied to the wheels where the rubber hits the road. Every action produces a reaction so the torque to the wheels is also forcing the car out of level. (farm tractors and dragsters can lift their front tires right off the ground from the torque at the rear wheels)
    Because the car is not level to the same degree your bauble is showing it like the bubble in a level vial would.
    Last edited by dan hunter; May 19th, 2014 at 11:00 PM.
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    Quote Originally Posted by marcbo View Post
    On those occasions, I observe the bauble thingy. Travelling in a perfectly straight line, at 110 kph, on what is, to the limits of my perception, a perfectly even road surface, the bauble is no longer directly over the ‘P’. It has drifted (is that the right word ?) about one centimetre towards the rear of the car, in the opposite direction of the cars travel.
    The car's wheels (low) are pushing against drag (which is centered higher.) This pitches the car slightly. In addition, the force the wheels are exerting against the frame of the car slightly changes the geometry of the suspension, which also changes the pitch of the car.
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    Thank you both. I should have stated earlier, that the car is a Subaru AWD, ie, constant 4WD. It is reasonable to assume then, that on a dead straight, level motorway, cruising at a comfortable speed, the car would be level. I can't see any reason for it not to be as level as when at rest.
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    PS - I just thought that one way to sort it out would be to firmly afix a spirit level somewhere in the car whilst it is ar rest, note carefully the horizontal, leave it in situ, and then compare it during the journey, detailed above. I suppose I could easily do this, but I'm not due for another trip for a few weeks, and certainly not until next school holidays when my partner in crime, the 13 year old nosey boy, will be able to accompany me .. I can't perform scientific experiments while hurtling down the freeway at 128 .. err, 110 kph.

    But, I am almost certain that no 'car off level' situation would be the cause.
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    Quote Originally Posted by marcbo View Post
    Thank you both. I should have stated earlier, that the car is a Subaru AWD, ie, constant 4WD. It is reasonable to assume then, that on a dead straight, level motorway, cruising at a comfortable speed, the car would be level.
    That may seem reasonable but it ignores the displacement of the two forces. Do the force diagram. There is net torque on the car trying to pitch its nose up. If you put a big carrier on the roof it will pitch back more. If you drive at a very high altitude at the same speed it will pitch back less. Which wheels are driven has very little to do with it.
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    Quote Originally Posted by marcbo View Post
    Thank you both. I should have stated earlier, that the car is a Subaru AWD, ie, constant 4WD. It is reasonable to assume then, that on a dead straight, level motorway, cruising at a comfortable speed, the car would be level. I can't see any reason for it not to be as level as when at rest.
    AWD vehicles have a viscous coupling between the front and rear wheels, so it's basically a front wheel drive until the drive wheels slip, creating some speed differential between front and rear. As Dan and Bill pointed out, there will be a torque couple between the thrust of the wheels and the drag acting on the body of the car that will tend to point the nose of the car up.
    PS - I just thought that one way to sort it out would be to firmly afix a spirit level somewhere in the car whilst it is ar rest, note carefully the horizontal, leave it in situ, and then compare it during the journey, detailed above. I suppose I could easily do this, but I'm not due for another trip for a few weeks, and certainly not until next school holidays when my partner in crime, the 13 year old nosey boy, will be able to accompany me .. I can't perform scientific experiments while hurtling down the freeway at 128 .. err, 110 kph.

    But, I am almost certain that no 'car off level' situation would be the cause.
    The spirit level will be affected by acceleration, just like the plumb bob, so I don't think it would prove much more than your plumb bob already shows you, which is that the car isn't level.
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  67. #66  
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by marcbo View Post
    On those occasions, I observe the bauble thingy. Travelling in a perfectly straight line, at 110 kph, on what is, to the limits of my perception, a perfectly even road surface, the bauble is no longer directly over the ‘P’. It has drifted (is that the right word ?) about one centimetre towards the rear of the car, in the opposite direction of the cars travel.
    The car's wheels (low) are pushing against drag (which is centered higher.) This pitches the car slightly. In addition, the force the wheels are exerting against the frame of the car slightly changes the geometry of the suspension, which also changes the pitch of the car.
    SNAP! I had exactly the same thought. The car may squat slightly overcoming air resistance.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by marcbo View Post
    Thank you both. I should have stated earlier, that the car is a Subaru AWD, ie, constant 4WD. It is reasonable to assume then, that on a dead straight, level motorway, cruising at a comfortable speed, the car would be level.
    That may seem reasonable but it ignores the displacement of the two forces. Do the force diagram. There is net torque on the car trying to pitch its nose up. If you put a big carrier on the roof it will pitch back more. If you drive at a very high altitude at the same speed it will pitch back less. Which wheels are driven has very little to do with it.
    Hi billvon;
    Not sure why the car would be trying to pitch it's nose up. No carrier on top, no high altitude.
    Modern cars, Subarus for sure, have excellent stability control. I have never really noticed the car being 'pitched' up or down in the scenario I've described.

    As I said earlier, I've played around with this phenomenon often, whilst cruising on the motorway - just out of curiosity more than anything.

    Several times, I tried the following.

    I accelerated to about 130kph (safely, no cops, no other cars in sight). The pendulum (let's call it that - see following) moved a tiny bit further towards the rear of the car, ie, opposite direction of cars travel. I then eaased off the gas, and put the car n nuetral. After an initial 'bump' when the car entered nuetral, the pendulum maintained it's position. There is even more reason to suppose now, that there was no extraneous force acting on it from the wheels. Over the space of 40 seconds or so, the car slowed down to about 60kph, and as it did, the pendulum gradually reverted closer to vertical, ie, came closer and closer to being in the 'over the P position.
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    Quote Originally Posted by Harold14370 View Post
    Quote Originally Posted by marcbo View Post
    Thank you both. I should have stated earlier, that the car is a Subaru AWD, ie, constant 4WD. It is reasonable to assume then, that on a dead straight, level motorway, cruising at a comfortable speed, the car would be level. I can't see any reason for it not to be as level as when at rest.
    AWD vehicles have a viscous coupling between the front and rear wheels, so it's basically a front wheel drive until the drive wheels slip, creating some speed differential between front and rear. As Dan and Bill pointed out, there will be a torque couple between the thrust of the wheels and the drag acting on the body of the car that will tend to point the nose of the car up.
    PS - I just thought that one way to sort it out would be to firmly afix a spirit level somewhere in the car whilst it is ar rest, note carefully the horizontal, leave it in situ, and then compare it during the journey, detailed above. I suppose I could easily do this, but I'm not due for another trip for a few weeks, and certainly not until next school holidays when my partner in crime, the 13 year old nosey boy, will be able to accompany me .. I can't perform scientific experiments while hurtling down the freeway at 128 .. err, 110 kph.

    But, I am almost certain that no 'car off level' situation would be the cause.
    The spirit level will be affected by acceleration, just like the plumb bob, so I don't think it would prove much more than your plumb bob already shows you, which is that the car isn't level.
    I'm not sure if what you say about AWD's applies to Subarus.

    In any case, if it acted more like a front wheel drive, it would pitch downwards, not upwards. This is easy to see - accelerate in a rear wheel drive and the front end pitches up. Accelerate in a front wheel drive, and it pitches down.

    Yes, I see what you say about the spirit level probably not proving much.

    But please se my next post.
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    I've done a bit of searching around concerning this, as I don't think focus has been given here, to the phenomenon that I'm trying to get to.

    Surprisingly (or perhaps rather unsurprisingly) this phenomenon has not escaped the notice of others, and has been canvassed by many at length. For instance ..

    http://askthephysicist.com/classical%20mechanics.html#accpendulum

    QUESTION:
    I had asked you a question and you had answered it. To illustrate your point, you had quoted an example that a pendulum hanging from the ceiling of a car moving with a uniform acceleration makes an angle with the vertical. Now we have been taught in our course as well. We have also learnt that tangent of the angle is equal to a/g. My question is that will that pendulum exhibit uniform oscillations if it is displaced from its normal position?
    ANSWER:
    I presume that by "its normal position" you mean its new equilibrium position off the vertical. The answer to your question is that it will exhibit oscillations about this position; the period, though, will not be given by T≈2π√(L/g) but rather by T'≈2π√[L/√(g2+a2)]. This is most easily understood by introducing a fictitious force ma opposite the direction of the acceleration. Now you can see that the force exerting a torque on this pendulum has a magnitude of m√(g2+a2) rather than mg as in the unaccelerated pendulum. So it is just like the usual pendulum analysis with a somewhat larger acceleration due to gravity.

    Now, the nature of my enquiry is NOT about uniform oscillations, but simply, what is that force that puts the pendulum off the vertical in the cicrumstances I've described ? The above certainly suggests that it does go off the vertical as I've observed.

    See my underlined above! THIS is what I'm getting at, although all the equations, math, etc, are beyond me.

    I searched (OK, googled) 'Pendulum in accelerated car' and the replies are legion. More notably, it seems this has been canvassed a good deal in physics forums, note;

    Pendulum hanging in a car

    Pendulum in an accelerating car

    .. much there about some psuedo force, or ficticious force ..

    So THAT'S what I'm getting at - should have searched it earlier.

    My guess - it is simply the pendulums inertia - tending to stay at rest whilst being dragged along by the thread. It is natural, instinctive even, to visualise it, and suppose that it would lag behind a little.

    Last edited by marcbo; May 20th, 2014 at 08:42 PM. Reason: spelling
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by billvon View Post
    Quote Originally Posted by marcbo View Post
    On those occasions, I observe the bauble thingy. Travelling in a perfectly straight line, at 110 kph, on what is, to the limits of my perception, a perfectly even road surface, the bauble is no longer directly over the ‘P’. It has drifted (is that the right word ?) about one centimetre towards the rear of the car, in the opposite direction of the cars travel.
    The car's wheels (low) are pushing against drag (which is centered higher.) This pitches the car slightly. In addition, the force the wheels are exerting against the frame of the car slightly changes the geometry of the suspension, which also changes the pitch of the car.
    SNAP! I had exactly the same thought. The car may squat slightly overcoming air resistance.
    exchemist - I think I mucked an edit up .. most of what I posted dissapeared. I'll try to recreate it.

    I don't think it did squat at all - never noticed this.

    In any case, front end sqatting down (or rear end coming up - same thing) to overcome air resistance, would result in the pendulum moving in the other direction. See if you can visualise it.
    Last edited by marcbo; May 20th, 2014 at 09:02 PM. Reason: changed last paragraph
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    Marcbo, let me say how nice it is to see someone actually researching their question in addition to asking it here. Too many posters ask the question and then sit back, expecting to be spoon fed an answer.

    Well done.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

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    I don't think inertia will give you a CONSTANT deflection? You will only see a deflection due to inertia while accelerating or decelerating.

    I think the others are right; your car must be pitching up slightly. The force of the engine is applied forwards down at the road surface by the wheels. The drag of the air you are driving through is applied rearwards to the car body which is above the wheels. These two forces will rotate the car; by lifting the body slightly at the front and pushing down slightly on the rear.

    Some cars, e.g. some Jaguars have anti squat rear suspension, so the effect might not occur with those.

    OB
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    Quote Originally Posted by AlexG View Post
    Marcbo, let me say how nice it is to see someone actually researching their question in addition to asking it here. Too many posters ask the question and then sit back, expecting to be spoon fed an answer.

    Well done.
    Hi AlexG, thanks.

    Exchemist, please se substantial edit in my reply to you, above.
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    Quote Originally Posted by marcbo View Post


    I'm not sure if what you say about AWD's applies to Subarus.

    In any case, if it acted more like a front wheel drive, it would pitch downwards, not upwards. This is easy to see - accelerate in a rear wheel drive and the front end pitches up. Accelerate in a front wheel drive, and it pitches down.
    I don't know why you would expect the front of a front wheel drive car to lower because the torque on the wheels is in the same direction in both cases.
    The weight transfer from the torque still moves from the front to the rear of the vehicle.
    Because you are working against air resistance your car still requires the motor to supply force to the wheels to stay moving so even if you are driving at a steady speed you still have a load transfer from the front to the rear wheels.

    http://en.wikipedia.org/wiki/Weight_transfer
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    Quote Originally Posted by dan hunter View Post
    Quote Originally Posted by marcbo View Post


    I'm not sure if what you say about AWD's applies to Subarus.

    In any case, if it acted more like a front wheel drive, it would pitch downwards, not upwards. This is easy to see - accelerate in a rear wheel drive and the front end pitches up. Accelerate in a front wheel drive, and it pitches down.
    I don't know why you would expect the front of a front wheel drive car to lower because the torque on the wheels is in the same direction in both cases.
    The weight transfer from the torque still moves from the front to the rear of the vehicle.
    Because you are working against air resistance your car still requires the motor to supply force to the wheels to stay moving so even if you are driving at a steady speed you still have a load transfer from the front to the rear wheels.

    Weight transfer - Wikipedia, the free encyclopedia
    It was a simple observation, and I thought, a reply to a previous question.

    Rephrase; from a standing start, I hit the gas on a RWD - the front end goes up momentarily. In a FrontWD, the front end goes down momentarily. I know this because I've observed it multiple times in decades of driving.

    Concering motive force from wheels, etc, see my post above when I had the car in nuetral.

    I don't really want to get bogged down with this. It should be noted that many have canvassed this before, it seems. Did you see the links above ? Also, see

    https://ca.answers.yahoo.com/questio...1175648AAY7bMw

    Not only is it a recognised phenomenon, educationalists are using it as a 'given' and having students solve for rate of acceleration.

    Please read each of the entries (there's only a few) in the above link and you'll see what I mean.
    Last edited by marcbo; May 20th, 2014 at 11:26 PM.
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    Quote Originally Posted by One beer View Post
    I don't think inertia will give you a CONSTANT deflection? You will only see a deflection due to inertia while accelerating or decelerating.

    I think the others are right; your car must be pitching up slightly. The force of the engine is applied forwards down at the road surface by the wheels. The drag of the air you are driving through is applied rearwards to the car body which is above the wheels. These two forces will rotate the car; by lifting the body slightly at the front and pushing down slightly on the rear.

    Some cars, e.g. some Jaguars have anti squat rear suspension, so the effect might not occur with those.

    OB
    Hi Ob - not ignoring your post - just can't see anything there that I haven't responded to already.

    Oops, OK, except for your 1st line.

    OK, you accept that there is deflection during acceleration to 110kph. What happens then to that delfection ? I maintain the speed at exactly 110kph (with the aide of a very good cruise controller). You say the pendulum moves back to the vertical ? If so, why ?
    Last edited by marcbo; May 20th, 2014 at 11:24 PM. Reason: spelling, format
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    So Marcbo, does the front end of your Subaru rise when you put the brakes on too?

    Watch carefully
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    Hi Dan - does it really matter ?

    I recall driving a rear wheel drive car - a Ford Falcon, that momentarily pitches upwards when taking off. I recall driving a front wheel drive car, a Kia Sportage (they're quite high) where the front end dipped momentarily when taking off. Is this such an unknown thing ? I wouldn't have thought so.

    What does race car braking (or any braking) have to do with the subject at hand ?

    I don't really want to go round in ever increasing circles of irrelevancies (not saying you're doing that).

    I want to explore the phenomenon as stated, paraphrased ..

    110kph, dead level, even, straight road (to the limits of my perception), no air turbulance in car. A pendulum in car has moved slightly off the vertical, in the opposite direction of travel. Manually pushed back to the vertical, it immediately resumes it's off vertical position when released.

    I believe it has nothing to do with pitching, braking, aerodynamics, etc. S

    ee the various links I've provided where this is discussed by physicists, educationalists, etc.

    Do they mean nothing ?
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    Some of what you fellows have digressed into was part of the reasons the disk brake locations were changed in the mid 1970's..
    ~ Racing and later street machine Motorcycles progressed into disk brakes and they tended to mount them forward of the forks.
    When breaking from speed the frond end dived down as the fork came under compression of weight transfer.. It was later after race testing found that by shifting the calipers to a location under/ behind the fork that the dive was eliminated.. Greater stability.
    ~ This question is nothing to do with this.. To your pendulum question; The movement backwards is only evident during acceleration.. as the pivot point is accelerated forward. Hit the breaks to see it go forward.. ( and please watch the road / not the pendulum..
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  81. #80  
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    Quote Originally Posted by marcbo View Post

    QUESTION:
    I had asked you a question and you had answered it. To illustrate your point, you had quoted an example that a pendulum hanging from the ceiling of a car moving with a uniform acceleration makes an angle with the vertical. Now we have been taught in our course as well. We have also learnt that tangent of the angle is equal to a/g.
    If the tangent of the angle is a/g, and if you are going at a constant speed, then a=0, the tangent of a/g = 0, and your hanging thing hangs straight down.

    My question is that will that pendulum exhibit uniform oscillations if it is displaced from its normal position?
    ANSWER:
    I presume that by "its normal position" you mean its new equilibrium position off the vertical. The answer to your question is that it will exhibit oscillations about this position; the period, though, will not be given by T≈2π√(L/g) but rather by T'≈2π√[L/√(g2+a2)]. This is most easily understood by introducing a fictitious force ma opposite the direction of the acceleration. Now you can see that the force exerting a torque on this pendulum has a magnitude of m√(g2+a2) rather than mg as in the unaccelerated pendulum. So it is just like the usual pendulum analysis with a somewhat larger acceleration due to gravity.
    When they discuss an equilibrium position off the vertical, they are discussing uniform acceleration, not uniform speed.
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  82. #81  
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    OK, during acceleration, inertia causes the movement of the pendulum that you see. When the acceleration stops*, the pendulum will not be deflected any more by the acceleration (f = ma?). So the deflection must be due to something else. The pendulum is inside the car, so there is no drag from the air rushing past to displace it.

    You dismiss the car aerodynamics, but consider this. Imagine a small four wheeled trolley with a large piece of board mounted across the trolley vertically. A piece of rope is attached to the front of the trolley and you set off running, pulling the trolley behind you. As you speed up, the wind against the board will cause the front wheels to lift up. The vehicle will experience similar forces, but since it has suspension, the wheels will not leave the ground, but it will move on its springs.

    Does this describe what you are seeing do you think?


    *Obviously, the absence of acceleration does not imply the absence of movement!
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  83. #82  
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    Quote Originally Posted by marcbo View Post
    Not sure why the car would be trying to pitch it's nose up. No carrier on top, no high altitude.
    Again do the force diagram. Wheels push from the bottom of the car; drag acts roughly through the center. This will pitch the car backwards. As you reduce drag (higher altitude) this will happen less. As you increase drag (add a carrier) then this will happen more.
    Modern cars, Subarus for sure, have excellent stability control. I have never really noticed the car being 'pitched' up or down in the scenario I've described.
    It's not something you'd notice; it's pretty minor. It also has nothing to do with stability control. With true active suspensions you can cancel this out, but most cars do not have true active suspensions.
    I accelerated to about 130kph (safely, no cops, no other cars in sight). The pendulum (let's call it that - see following) moved a tiny bit further towards the rear of the car, ie, opposite direction of cars travel.
    Agreed. That's what you would expect. Thrust and drag increase and thus the pitch angle increases.
    I then eaased off the gas, and put the car n nuetral. After an initial 'bump' when the car entered nuetral, the pendulum maintained it's position.
    Now you have eliminated the thrust but you still have the drag. Your only "thrust" is now momentum. Momentum will act along the center of gravity. If the center of drag is higher than the center of gravity I would expect to see what you describe. (In most cars this is true since the top half is draggy but light.) A caveat her is that since you are decelerating you have more than one force acting on your pendulum so you have to take that into account.
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  84. #83  
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    Quote Originally Posted by Harold14370 View Post
    Quote Originally Posted by marcbo View Post

    QUESTION:
    I had asked you a question and you had answered it. To illustrate your point, you had quoted an example that a pendulum hanging from the ceiling of a car moving with a uniform acceleration makes an angle with the vertical. Now we have been taught in our course as well. We have also learnt that tangent of the angle is equal to a/g.
    If the tangent of the angle is a/g, and if you are going at a constant speed, then a=0, the tangent of a/g = 0, and your hanging thing hangs straight down.

    My question is that will that pendulum exhibit uniform oscillations if it is displaced from its normal position?
    ANSWER:
    I presume that by "its normal position" you mean its new equilibrium position off the vertical. The answer to your question is that it will exhibit oscillations about this position; the period, though, will not be given by T≈2π√(L/g) but rather by T'≈2π√[L/√(g2+a2)]. This is most easily understood by introducing a fictitious force ma opposite the direction of the acceleration. Now you can see that the force exerting a torque on this pendulum has a magnitude of m√(g2+a2) rather than mg as in the unaccelerated pendulum. So it is just like the usual pendulum analysis with a somewhat larger acceleration due to gravity.
    When they discuss an equilibrium position off the vertical, they are discussing uniform acceleration, not uniform speed.
    Hi Harold - noted, particularly last sentence. I think that's what I got confused about, and then got exited about the linked articles.
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    Quote Originally Posted by One beer View Post
    OK, during acceleration, inertia causes the movement of the pendulum that you see. When the acceleration stops*, the pendulum will not be deflected any more by the acceleration (f = ma?). So the deflection must be due to something else. The pendulum is inside the car, so there is no drag from the air rushing past to displace it.

    You dismiss the car aerodynamics, but consider this. Imagine a small four wheeled trolley with a large piece of board mounted across the trolley vertically. A piece of rope is attached to the front of the trolley and you set off running, pulling the trolley behind you. As you speed up, the wind against the board will cause the front wheels to lift up. The vehicle will experience similar forces, but since it has suspension, the wheels will not leave the ground, but it will move on its springs.

    Does this describe what you are seeing do you think?


    *Obviously, the absence of acceleration does not imply the absence of movement!
    Small four wheeled trolley .. LOL, that's about my paygrade in physics I suppose.

    But yes, I've been thinking a lot about what you and others have said.

    Unless I've discovered a new law of physics, it must be that I should NOT dismiss aerodynamics so quickly. Even in a 'symetrical AWD' (as Suba descibes itself) there may be, in fact most probably is, a slight change in attitude sufficent for the phenomenon to occur.

    I've also been thinking there may be some confirmation bias on my part .. probably coupled with the act of me imperceptably sinking a little further into the driver seat at high cruising speeds .. all or any part thereof serve to create some illusion.

    Thanks for taking the time, One beer.
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  86. #85  
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by marcbo View Post
    Not sure why the car would be trying to pitch it's nose up. No carrier on top, no high altitude.
    Again do the force diagram. Wheels push from the bottom of the car; drag acts roughly through the center. This will pitch the car backwards. As you reduce drag (higher altitude) this will happen less. As you increase drag (add a carrier) then this will happen more.
    Modern cars, Subarus for sure, have excellent stability control. I have never really noticed the car being 'pitched' up or down in the scenario I've described.
    It's not something you'd notice; it's pretty minor. It also has nothing to do with stability control. With true active suspensions you can cancel this out, but most cars do not have true active suspensions.
    I accelerated to about 130kph (safely, no cops, no other cars in sight). The pendulum (let's call it that - see following) moved a tiny bit further towards the rear of the car, ie, opposite direction of cars travel.
    Agreed. That's what you would expect. Thrust and drag increase and thus the pitch angle increases.
    I then eaased off the gas, and put the car n nuetral. After an initial 'bump' when the car entered nuetral, the pendulum maintained it's position.
    Now you have eliminated the thrust but you still have the drag. Your only "thrust" is now momentum. Momentum will act along the center of gravity. If the center of drag is higher than the center of gravity I would expect to see what you describe. (In most cars this is true since the top half is draggy but light.) A caveat her is that since you are decelerating you have more than one force acting on your pendulum so you have to take that into account.
    Thanks billvon - as stated above, I think I'm getting the message ..

    Cheers !
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  87. #86  
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    Quote Originally Posted by astromark View Post
    Some of what you fellows have digressed into was part of the reasons the disk brake locations were changed in the mid 1970's............. they tended to mount them forward of the forks.
    When breaking from speed the frond end dived down as the fork came under compression of weight transfer.. It was later after race testing found that by shifting the calipers to a location under/ behind the fork that the dive was eliminated.. Greater stability.

    Thanks, Astromark, I have always wondered about this, because mounting the calipers behind the forks needs a beefier mounting than if they are mounted in front.


    OB
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