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Thread: fastest 1/4 mile

  1. #1 fastest 1/4 mile 
    Forum Ph.D. william's Avatar
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    warning: MATH ALERT

    In 1989, Shirley Muldowney set a new record for the fastest 1/4 mile by a wheel-driven car.

    If I told you that the coefficient of static friction between her tires and the road was

    mu = 3.34,

    what was her best possible time?



    Cheers,
    william

    Footnote:
    Her record has been broken since, but I'm too lazy to look up the new number and owner of that number.


    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  3. #2  
    Forum Sophomore L.E.A.P.'s Avatar
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    Quote Originally Posted by william
    Footnote:
    Her record has been broken since, but I'm too lazy to look up the new number and owner of that number.
    May I just add something by the way?
    What's funny is hat you took the time of writing... let me see... 1, 2, 3, 4... 25 words wrather then writing 3!

    By the way, long time no see, HI EVERYONE, I'M BACK!!!


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  4. #3  
    Forum Ph.D. william's Avatar
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    Would it help to spur you guys to solve this if I said that all the math and physics you need to solve this can be found in an introductory algebra-based physics text?

    cheers
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  5. #4  
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    What was the mass of the car, what was the power of the engine? Are you sure you've given us enough to work with here?
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  6. #5  
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by billiards
    What was the mass of the car, what was the power of the engine? Are you sure you've given us enough to work with here?
    Yes I have given you enough. That is the interesting thing about this problem!

    cheers,
    wm
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  7. #6  
    Forum Professor river_rat's Avatar
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    I get the best time to be (2 s \ (g mu<sub>s</sub>))<sup>1/2</sup> where

    • s is the distance travelled (400 m in problem)
    • g is gravitiational acceleration (lets say 9.8 m.s^2)
    • mu<sub>s</sub> is the coeff. of static friction (3.34)


    This gives a minimum time of around 4.9 seconds or an average of almost 300km/h

    Am i right?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  8. #7  
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by river_rat
    I get the best time to be (2 s \ (g mu<sub>s</sub>))<sup>1/2</sup> where

    • s is the distance travelled (400 m in problem)
    • g is gravitiational acceleration (lets say 9.8 m.s^2)
    • mu<sub>s</sub> is the coeff. of static friction (3.34)


    This gives a minimum time of around 4.9 seconds or an average of almost 300km/h

    Am i right?
    Excellent!
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  9. #8  
    Forum Professor river_rat's Avatar
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    Lol - two years of university physics have their merits

    Though i had to show someone today how to work out moments of inertia - damn if i could remember what the definition of that was!
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  10. #9  
    Cooking Something Good MacGyver1968's Avatar
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    Shirley's time in 1989 was 4.97 seconds with a top speed of 284mph/457kph. So your pretty damn close. Her best time was in 2003 with a time of 4.579 @327mph/526kph. (I guess she increased her traction )
    The best time ever for top fuel is 4.437 seconds by Anthony Schumacher and the fastest speed is 336.15mph/540kph by Tony Schumacher. Damn thats fast!
    Fixin' shit that ain't broke.
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  11. #10  
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by MacGyver1968
    Shirley's time in 1989 was 4.97 seconds with a top speed of 284mph/457kph. So your pretty damn close. Her best time was in 2003 with a time of 4.579 @327mph/526kph. (I guess she increased her traction )
    The best time ever for top fuel is 4.437 seconds by Anthony Schumacher and the fastest speed is 336.15mph/540kph by Tony Schumacher. Damn thats fast!
    Thanks for the updated numbers. I was too lazy to look them up myself (and apparently so was the author of the text book where I took the numbers from...).

    cheers
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  12. #11  
    Forum Ph.D. william's Avatar
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    Quote Originally Posted by MacGyver1968
    ... (I guess she increased her traction )...
    Yes! She would have had to. Otherwise the wheels would just spin and she couldn't improve her time.

    That is one of the interesting things about this question. I see a lot of attention being devoted to how to increase horsepower and such but I have to wonder how much attention is devoted to traction for the general drag-racer. We see here that it definitely is a limiting factor.

    River_Rat didn't take all the fun out of this thread. He still left it a mystery to the rest of you as to how he got his formula....

    Still fun to be had!

    Cheers,
    william
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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