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Modern Physics... relativistic

by irony of truth
Tags: modern, physics, relativistic
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irony of truth
#1
Mar10-05, 11:55 AM
P: 91
How much mass does an electron gain if it is accelerated to an energy of 500 MeV?

My solution:

I am using the mass of the electron in terms of "energy units"... that is
m_e = 0.511 MeV/c^2 where c is the speed of light.

The total energy is E = Eo + ke, where ke is kinetic energy

Am I right here... mc^2 = m_ec^2 + ke?

I mean.. should my E be mc^2/(1 - v^2/c^2)^(1/2)? I am confused.. but
if I were to use that "relativistic" formula, I am not given the value of v.

Then m = m_e + ke/c^2.

Let m_e = 0.511 MeV/c^2 and ke = 500MeV

m = 500.511 MeV/c^2

Converting this mass to kilograms results to m = 8.9 x 10^-28 kg.
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Gamma
#2
Mar10-05, 02:08 PM
Gamma's Avatar
P: 333
E = mc^2 = m_ec^2 + ke?
is correct



should my E be mc^2/(1 - v^2/c^2)^(1/2)?

THis is right if that m is the rest mass of the electron/particle.

[tex] E = \gamma m_0 c^2 [/tex]


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