Question

Consider an electron which has been  accelerated from rest through a potential difference of 500kV. Find a) Its kinetic energy, b.) its rest energy, c.) its total energy, d.) its mass and e.) its speed.

Answer 1

a)

$E_k=eU=0.5~MeV,$

b)

$E_0=mc^2=0 .512~MeV,$

c)

$E=E_k+E_0=1~MeV,$

d)

$m=\frac E{c^2}=1.8\cdot10^{-30}~kg,$

e)

$v=c\sqrt{1-\frac{m_0^2}{m^2}}=0.87c.$