Question

The dynamic mass of electron having rest mass $m_0$ and moving with speed $0.8c$ is :

• A. $0.6m_0$
• B. $0.8m_0$
• C. $\frac{5}{3}{m}_o$
• D. $1.25m_0$

Answer 1

The correct option is C $\frac{5}{3}{m}_o$

Mass of the moving electron is,

$m=\frac{m_0}{\sqrt{\left(1-\frac{v^2}{c^2}\right)}}$

$=\frac{m_0}{\sqrt{\left(1-\frac{{\left(0.8c\right)}^2}{c^2}\right)}}$

$=\frac{m_0}{\sqrt{\left(0.36\right)}}$

$=\frac{m_0}{0.6}$

$=\frac{5m_0}{3}$

Thus mass of the moving electron is $\frac{5m_0}{3}$.