Is mass conserved in terms of Special Realitivity

[DODGEVIPER13]

Homework Statement

Is mass a conserved quantity under Special Realitivity?

Homework Equations

E=mc^2

The Attempt at a Solution

Total energy is always conserved in an isolated closed system, and since mass is just another form of energy, then mass would be conserved in a realtavistic situation right?

 

[phinds]

I'm not sure what SR and mass have to do with each other but certainly if you use E=mc^2 you are specifically saying that mass does NOT have to be conserved because you can turn it into energy.

 

[DODGEVIPER13]

But being that energy is neither created nor destoryed would transformation of the Mass efect the amounnt of mass you have because I would think it would remain constant?

 

[phinds]

But being that energy is neither created nor destoryed would transformation of the Mass efect the amounnt of mass you have because I would think it would remain constant?

Huh ?

Energy is created and mass is destroyed. How do you think an atom bomb works?

EDIT: perhaps a more pertinent question rather than one about the bomb would be, what do you think E=mc^2 MEANS ?

 

[DODGEVIPER13]

Total Energy = (Rest Mass)(Speed of light in a vacumm)^2. and I believe it states the equivalence between energy and mass.

 

[phinds]

Total Energy = (Rest Mass)(Speed of light in a vacumm)^2. and I believe it states the equivalence between energy and mass.

Right. Which means mass is NOT conserved. Doesn't that answer your question?

 

[DODGEVIPER13]

yes thanks

 

[HallsofIvy]

"mass-energy", of course, is conserved.

 

[DODGEVIPER13]

thanks Halls so it is conserved

 

[phinds]

thanks Halls so it is conserved

And what do you mean by "it". Your original question was "is mass conserved". The answer to that is NO, so if the above refers to mass, then NO, it is not conserved.

You seem to have some need to hear that mass is conserved. It isn't. As Ivy said, mass-energy IS conserved.

 

[vela]

You should also realize that when physicists refer to mass, they're talking about the rest or invariant mass of an object.

Journalists and other laypersons have an affinity for the idea of relativistic mass because it sounds cool to say the mass of an object changes with its speed. Relativistic mass, however, is really just the relativistic energy of the object divided by the constant c², so you might as well just talk about the object's energy instead of its (relativistic) mass. It just doesn't sound as cool to say that an object's energy increases as it speeds up.