Question

Rest mass energy of an electron is 0.54 $MeV$. If velocity of the electron is $0.8c$, then kinetic energy of the electron is

• A. 0.36 $MeV$
• B. 0.41 $MeV$
• C. 0.48 $MeV$
• D. 1.32 $MeV$

Answer 1

The correct option is A 0.36 $MeV$

$m_0{c}^2=0.54MeVK.E.=mc{\text{'}}^2-m_0{c}^2$
and $m=\frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}=\frac{m_0}{\sqrt{1-{(0.8)}^2}}=\frac{m_0}{0.6}E=mc{\text{'}}^2\mathrm{Here}c\text{'}\mathrm{is}\mathrm{the}\mathrm{velocity}\mathrm{of}\mathrm{mass}=0.8c=\frac{m_0}{0.6}{(0.8c)}^2=0.9MeVK.E=(0.9-0.54)=0.36MeV$