Einstein's equation of E = mc^2 says that matter and energy are equivalent. Does this mean that, since matter has mass, the more energy a system has the heavier it is? Take an ordinary object for example, say a sheet of metal. If you heat this sheet of metal up, will it weigh more?

Energy has the ability to bend space as well as matter.

Einstein's equation of E = mc^2 says that matter and energy are equivalent. Does this mean that, since matter has mass, the more energy a system has the heavier it is? Take an ordinary object for example, say a sheet of metal. If you heat this sheet of metal up, will it weigh more?

 

Yes, but you need to be measuring in the same frame (translational KE doesn't increase the mass in the object's own frame)

I`m not wanting to hijack the thread or anything, but I have a quick question if it`s ok with the OP.

 

Swansont, your post reads to me that the object in it`s own frame "doesn`t know" it`s increased in mass, but to an external frame it has, (my own wording).

 

so how come heat rises?

I`m not wanting to hijack the thread or anything' date=' but I have a quick question if it`s ok with the OP.

 

Swansont, your post reads to me that the object in it`s own frame "doesn`t know" it`s increased in mass, but to an external frame it has, (my own wording).

 

so how come heat rises?[/quote']

 

Because heat is in its own reference frame, moving relative to every other reference frame... You can then observe the difference from aother reference frame but the other frame knows no difference. Is what what you meant?

 

Cheers,

 

Ryan jones

I`m not wanting to hijack the thread or anything' date=' but I have a quick question if it`s ok with the OP.

 

Swansont, your post reads to me that the object in it`s own frame "doesn`t know" it`s increased in mass, but to an external frame it has, (my own wording).

 

so how come heat rises?[/quote']

 

I'm trying to differentiate this and head off the (almost) inevitible "relativistic mass" confusion. You have to measure mass in a well-defined reference frame to make a reasonable comparison. An object with added internal energy will have additional mass.

 

Heat rises because of density issues: PV=nRT or something like that, so hotter things take up more volume. Once you have that, you have a bouyancy force, from Archimedes' principle.

Einstein's equation of E = mc^2 says that matter and energy are equivalent. Does this mean that, since matter has mass, the more energy a system has the heavier it is? Take an ordinary object for example, say a sheet of metal. If you heat this sheet of metal up, will it weigh more?

 

Like the guy just said about relativistic mass, you can add energy to an object but only its relativistic mass increases, it's not like it will have more real mass and if you weighed it it'd be higher...

 

good example is light, light is completely made of energy, so it has no real mass, but it does have a relativistic mass

 

(If I said anything incorrect please correct to people who know what they're talking about lol)

Swansont, I think I`m with ya, the Mass increase is less than the Volume change, and so it`ll be relatively "lighter" than its original frame before heating,because it`s density will alter more.

Thanks, makes perfect sense now

Like the guy just said about relativistic mass' date=' you can add energy to an object but only its relativistic mass increases, [b']it's not like it will have more real mass and if you weighed it it'd be higher...

[/b]

good example is light, light is completely made of energy, so it has no real mass, but it does have a relativistic mass

 

(If I said anything incorrect please correct to people who know what they're talking about lol)

 

I think the object has more mass, more rest mass wrt it's rest frame, but it constituent particles or atoms or molecules do not wrt their rest frames.

Heat rises because of density issues: PV=nRT or something like that, so hotter things take up more volume. Once you have that, you have a bouyancy force, from Archimedes' principle.

 

Hey, that's a good point. So I guess the question should be stated "What would the scale read as you heat an object up above the Earth's atmosphere where there is no bouyancy force?"

Like the guy just said about relativistic mass' date=' you can add energy to an object but only its relativistic mass increases, it's not like it will have more real mass and if you weighed it it'd be higher...

 

good example is light, light is completely made of energy, so it has no real mass, but it does have a relativistic mass

 

(If I said anything incorrect please correct to people who know what they're talking about lol)[/quote']

 

Not really what I daid (or at least not what I intended to imply)

 

You have a lump of material (like U-235) and it has a mass m. Then it releases a bunch of energy (e.g. it fissions); you let it cool to the same temperature and it will have less mass than you started with. Some of that mass that was "lost" was in the form of heat, and the actual measurable mass of the material was higher originally than at the end of the experiment. So internal energy will show up as mass.

 

But if you now impart a speed to that object, and try and use the E=mc² argument, you are sort of comparing apples and oranges, since an observer moving with the mass doesn't see that increase. The second is a use of "relativistic mass" because you are lumping a kinetic energy term into the total energy, while the first example is not. Any inertial observer will agree what the mass of the material is before and after the experiment - it will be the rest mass of the material.