Total energy, mass, and momentum.

[Jchem]

An electron with speed 0.8c, has a rest energy of .51MeV.

What are its mass, its momentum, and its energy (including rest energy)?


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Ok, isn't it possible to get the three answers without using the .5MeV ?

I have 3 formulas for mass, momentum and total energy that don't use the .5Mev


but then I feel like I might be doing something wrong since they gave me the value.



Im not sure how to post the forumlas, but they are on this page

http://galileo.phys.virginia.edu/classes/252/energy_p_reln.html



thanks for any help

 

[vsage]

The rest energy is the $$m_0c^2$$ part of the formulas found on that page. Also, hyperphysics ( http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html ) is the #1 most helpful site I have found when I need to reference something. You will probably understand the formulas a little better if you look at the sections dedicated to relativistic energy there.

 

[OlderDan]

An electron with speed 0.8c, has a rest energy of .51MeV.

What are its mass, its momentum, and its energy (including rest energy)?


----------------------------------------------------------------------

Ok, isn't it possible to get the three answers without using the .5MeV ?

I have 3 formulas for mass, momentum and total energy that don't use the .5Mev


but then I feel like I might be doing something wrong since they gave me the value.



Im not sure how to post the forumlas, but they are on this page

http://galileo.phys.virginia.edu/classes/252/energy_p_reln.html



thanks for any help

The only way to avoid using the given information is if you know the rest mass of the electron. Look at the E equation in the limit of zero velocity. What is it telling you?

OOPs too late again. It's still the right question, and now you have the answer

 

[dextercioby]

You don't need that 0.51 MeV.Just that

m_{el}~9.1*10^{-31}Kg.

Daniel.