View Full Version : Intertial and Gravitational Mass

2004-Sep-11, 01:38 PM
Well, there is no difference, but Those two are taken to be two different things.

But, what's the definition of mass ( in classical physics- forget Higgs for a moment). I have seen two until now- 1) m = F/a & 2) amount of matter in a substance. If we take the second definition , and take newtonian physics, and that gravity is a force, it is implied that acceleration produced by gravity will be equal to the acceleration in a moving frame ( The Principle of Equivalence ) . But at odds with General relativity, which says gravity is not a force.
Now we take the 1st definition. But, it's main drawback is that it doesn't give any sense to the word 'mass'. It cannot be defined unless we know a force which produces a certain acceleration in the body. Here, the Higgs boson enters. And the debate starts ( ' Anti-Higgs' ) .

Any way to remove all this and give a physical sense to the word 'Mass' .

Please correct me if I'm wrong.

2004-Sep-11, 03:53 PM
you can't have mass in the first dimension. Mass is closely correlated to matter, which has to have density, and therefore can only appear in the third dimension.
Also, if you're going to talk about F=ma, you'd better also think about p=mv.

2004-Sep-11, 06:25 PM
Originally posted by StarLab@Sep 11 2004, 03:53 PM
you can't have mass in the first dimension
I believe he wrote "1st definition", not "first dimension". His first definition was inertial mass, that is, the ratio of Force and acceleration.

2004-Sep-11, 08:05 PM
What about that p=mv equation. Is that another kind of "mass?"

2004-Sep-12, 12:19 AM
Baron Roland von Eotvos answered this question with over thirty years of data
in Budapest..

Inertia is what resists being set in motion..Gravitational mass deals with the
amount of curvature that space is being told to take on by a given mass. In a
Newtonian sense, gravitational mass deals with how much the center of Earth is
pullling on a given object toward its center..

An object with inertial mass and no gravitational mass, hanging at the end of some rope or thin fiber and whose axis is perpendicular to Earth, will be pulled straight out from the axis of Earth's spin..

An object with gravitational mass and no inertial mass will hang straight down,
pointing to Earth's center..

An object with both inertal and gravitational mass will show some angle of uprise..
If the angle of uprise is different from one substance to another, then the ratio of
inertial mass to gravitational mass differs from one substance to another..

Eotvos found that there is an angle of uprise and it is precisely the same for all
substances tested..The angle is the greatest at 45*N and 45*S latitude where it amounts to a tenth of a degree..

Read Wheeler's "A Journey into Gravity and Spacetime"..