Relativity and Inertia - An Exploration

[Dale]

So,in my frame of reference,for a body at rest, it appears to me to have a mass,which is a measure of inertia in (linear motion),so there must be someone else in relative (uniform)motion with me who actually sees this 'mass' as 'energy'...and in one particular frame there must be no mass at all,but only energy!

Maybe this will help. One of the most important concepts in SR is the four-momentum. The timelike component of the four momentum is proportional to the total energy or the relativistic mass. The spacelike components are the momentum, and the norm (magnitude) of the four-momentum is proportional to the rest mass.

Now, like all four-vectors the four-momentum Lorentz transforms like time and space do, and the norm is invariant. So this implies the following for a massive particle:
1) The rest mass is invariant (all frames agree)
2) The relativistic mass is minimized in the rest frame and is strictly greater in other frames
3) There is no frame where either mass goes to 0

 

[Alkemist]

Hi,
I'm new here,so I'm kinda nervous.

Anyway,I have a big question(big to me atleast!) about inertia.

I've been pondering what exactly this thing inertia is-why does a body have inertia just because it has a mass? What capability does "matter" in an object have to try and prevent external forces from acting on it?

I thought that Einstein's E=mcsquared might help-saying that mass has a certain amount of energy may mean that it has energy to oppose external forces--I'm not really sure.

On the moon where the gravitational forces are a lot weaker,its easier to lift an object,does it mean that it has less inertia. If it does, inertia is supposed to depend on mass only,so gravitational forces aren't supposed to affect it!

Please help!

Inertia is property of a material. I think you wanted to ask some thing else, right?