# as speed increases so does mass

• March 18th, 2007, 09:11 PM
shawngoldw
as speed increases so does mass
I don't understand why mass increases as speed does. Does volume also increase? Or gravity? I have a feeling the explanation is really math in which case simplify it as much as you can please. thanks.
• March 18th, 2007, 09:54 PM
pmb
mass increase
"I don't understand why mass increases as speed does. Does volume also increase? Or gravity? I have a feeling the explanation is really math in which case simplify it as much as you can please. thanks. "

The best I can do is to tell you that the cause is due to the nature of space and time and their transfrmation properties. The mathy stuff is here

http://www.geocities.com/physics_wor...rtial_mass.htm

Pete
• March 18th, 2007, 11:56 PM
necroforest
Here's how I understand it (correct me if I'm wrong...):

According to special relativity, E=MC^2. If you solve for M, you get: M=E/C^2. Note that as you go faster, you gain kinetic energy. However, this is equivalent to mass via the previous equation, so you also gain mass.
• March 19th, 2007, 12:39 AM
Re: mass increase
Quote:

Originally Posted by pmb
"I don't understand why mass increases as speed does. Does volume also increase? Or gravity? I have a feeling the explanation is really math in which case simplify it as much as you can please. thanks. "

The best I can do is to tell you that the cause is due to the nature of space and time and their transfrmation properties. The mathy stuff is here

http://www.geocities.com/physics_wor...rtial_mass.htm

Pete

hey he is talking about one body and you have posted a link which has details about momentum. I think it doesnot relate with the post.
I don't think mass changes. Might weight change which is relevant to the gravitation.
Correct me if I am wrong.
• March 19th, 2007, 08:26 AM
pmb
mass increase
"hey he is talking about one body and you have posted a link which has details about momentum. I think it doesnot relate with the post.
I don't think mass changes. Might weight change which is relevant to the gravitation.
Correct me if I am wrong."

You're wrong. (inertial) mass is defined as the ratio of momentum to speed. The link I gave you shows how to determine the mass of a moving body. Just because it uses other masses to do this task is of no concern since what you end up with is the mass of the particle of interest.

Best regards

Pete
• March 19th, 2007, 10:17 AM
Yes i think it's so.
• March 19th, 2007, 03:04 PM
shawngoldw
Quote:

Originally Posted by necroforest
Here's how I understand it (correct me if I'm wrong...):

According to special relativity, E=MC^2. If you solve for M, you get: M=E/C^2. Note that as you go faster, you gain kinetic energy. However, this is equivalent to mass via the previous equation, so you also gain mass.

possibly, but doesn't the kinetic energy get created by conversion from potential energy which the matter already possesses?
• March 19th, 2007, 03:17 PM
river_rat
Re: as speed increases so does mass
Quote:

Originally Posted by shawngoldw
I don't understand why mass increases as speed does. Does volume also increase? Or gravity? I have a feeling the explanation is really math in which case simplify it as much as you can please. thanks.

Relative to who? For a point particle its mass does not increase as it gains speed, its volume stays zero and gravity behaves normally - things are slightly more complicated for systems of particles.

I went into this in the Energy explained thread if you want to take a look. (I attached the quote)

Quote:

Relativistic mass is a horrid old school term for the "inertial mass" that an inertial observer would measure for a moving particle. As the particle moves faster and faster the inertial mass increases with out bound which puts a speed limit on how fast a particle can go, which happens to be the speed of light. Now this is related to energy, as the energy of the particle goes up its relativistic mass also increases, but it is not invariant (so two different observers can't agree on the relativistic mass, each measures their own) but it is additive (so the relativistic mass of two particles relative to one observer is just the sum of the relativistic masses of each one separately). The physics world would be a whole lot happier if the general public would expunge this idea from its mind, as it leads to a whole host of silly concepts (especially when combined with that other favourite of mass mad science, black holes)

Rest mass (or just plain mass) is the mass of any particle in its rest frame (or for a system where its center of mass is at rest or equivalently when its total energy is at a minimum) and this is the measure of "stuff" that makes up the particle in question. Rest mass doesn't change, and it is the thing people are referring two when they talk about the mass of a particle. It is invariant (so everyone measures the same rest mass) but is NOT additive in general (which makes it messy when dealing with systems of particles) as you cant find in general a reference frame in which every part of your system is at rest relative to you. In general, the m that appears in an equation in physics is this beast, for example the m in the equation E2 = m2c4 + pc2 is the rest mass of a particle (and this equation serves to define the rest mass of a system of particles btw)

Now here is the crux of the matter - relativistic mass and energy are intertwined, in fact relativistic mass is a measure of the energy of a system. But this link does not carry over to the invariant mass (or to be pedantic just plain mass) of a single particle. It's not all peaches and cream though as it does kind of carry over for a system of particles, as the energy content increases or decreases the mass of the system changes as given by E=mc2!
• March 19th, 2007, 10:35 PM
Keith
M=(gamma)m-----This is for things with non-zero rest mass
-m="invariant/rest mass" or whatever
-gamma=1/sqrt(1-((|v|^2)/c^2)
-v is the relative velocity
-c is the speed of light

so M=m/sqrt(1-((|v|^2)/c^2))

There you have it, as the absolute value of v increases, the dominator gets smaller, making M bigger.

Also, the limit as v approaches c is infinity because the denominator would approach zero.

:?:
• March 20th, 2007, 06:46 AM
leohopkins
Re: as speed increases so does mass
Quote:

Originally Posted by shawngoldw
I don't understand why mass increases as speed does. Does volume also increase? Or gravity? I have a feeling the explanation is really math in which case simplify it as much as you can please. thanks.

Mass increases as speed does because mass and energy are equivelant. Volume has nothing to do with mass. Take 1kg of water and boil it, its volume has increased, however the mass stays the same.

If something has extra speed, it has extra energy, therefore it has extra mass, and yes its gravitational pull also increases, along with a few other weird and wonderful effects. :)
• March 20th, 2007, 07:01 AM
Uclock
If physics does not understand what mass is or what gives an object mass then how do they know mass increases with velocity?
I realise the equations tell you that but after all they are only equations.

Tony
• March 20th, 2007, 07:39 AM
river_rat
Re: as speed increases so does mass
Quote:

Originally Posted by leohopkins
Quote:

Originally Posted by shawngoldw
I don't understand why mass increases as speed does. Does volume also increase? Or gravity? I have a feeling the explanation is really math in which case simplify it as much as you can please. thanks.

Mass increases as speed does because mass and energy are equivelant. Volume has nothing to do with mass. Take 1kg of water and boil it, its volume has increased, however the mass stays the same.

If something has extra speed, it has extra energy, therefore it has extra mass, and yes its gravitational pull also increases, along with a few other weird and wonderful effects. :)

Um, no no no no no!
• March 20th, 2007, 08:23 AM
leohopkins
Quote:

Originally Posted by Uclock
If physics does not understand what mass is or what gives an object mass then how do they know mass increases with velocity?
I realise the equations tell you that but after all they are only equations.

Tony

Nope, not equations. Observations too.

If you are travelling, lets say in a racing car, the faster you go the more mass you will have, you will feel "G" forces as you are pulled harder to the ground. What has actually happened is that your mass has increased.

I like to think of mass as being a property whereby a force is pushed outwards in all vectors from a spherical point, causing a stress on the fabric of space time, the more energy you give this sphere, the harder it will push in space-time.
• March 20th, 2007, 08:28 AM
Quote:

Originally Posted by leohopkins
If you are travelling, lets say in a racing car, the faster you go the more mass you will have, you will feel "G" forces as you are pulled harder to the ground. What has actually happened is that your mass has increased.

:shock:
• March 20th, 2007, 08:34 AM
Farsight
It's not a sphere, leo. It's a circle. Well actually it's more of a "moebius doughnut", but a circle will do. Imagine a "particle" that is made out of a travelling stress that is going round and round in a circle. In simple terms, this circle that's being traced out is your rest mass. Now push this circle along. The path now being traced is a spiral. That's your relativistic mass. Within it there's still that circular component which is "invariant". There's been a lot of debate about mass in physics. In general "mass" is taken to be rest mass. Personally I prefer to think in terms of relativistic mass because it better illustrates the link between mass and energy. Again, see MASS EXPLAINED for details. The model offered there really does work.
• March 20th, 2007, 08:36 AM
leohopkins
Quote:

Originally Posted by Farsight
It's not a sphere, leo. It's a circle. Well actually it's more of a "moebius doughnut", but a circle will do. Imagine a "particle" that is made out of a travelling stress that is going round and round in a circle. In simple terms, this circle that's being traced out is your rest mass. Now push this circle along. The path now being traced is a spiral. That's your relativistic mass. Within it there's still that circular component which is "invariant". There's been a lot of debate about mass in physics. In general "mass" is taken to be rest mass. Personally I prefer to think in terms of relativistic mass because it better illustrates the link between mass and energy. Again, see MASS EXPLAINED for details. The model offered there really does work.

Im not sure what a "moebius" doughnut is. do Krispy Kreme's do them ?

:lol:

Thats interesting, that the geometry of matter should fundamentally be self-congruent, whether it has rest mass or relativistic mass. Hmmm.... :shock:

(A formula one car weighs 3 times more travelling at top speed than it does at rest.)