Physics-
General
Easy
Question
Rest mass energy of an electron is 0.51 MeV. If this electron is moving with a velocity 0.8 c (where c is velocity of light in vacuum), then kinetic energy of the electron should be.
- 0.28 MeV
- 0.34 MeV
- 0.39 MeV
- 0.46 MeV
The correct answer is: 0.34 MeV
Given m0c2 = 0.51 MeV and v = 0.8 c
K.E. of the electron = mc2– m0c2
But 
Now, 
MeV = 0.85 MeV
\ K.E. = (0.85 – 0.51)MeV = 0.34 MeV
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