The percentage increase in the rest mass of an electron when it is moving at a speed of 0.6 c where c is the speed of light, is

Options

A. 0.52
B. 0.75
C. 0.25
D. 0.5

Answer

C

Explanation

`m=m_(0)/sqrt(1-v^(2)/c^(2))=m_(0)/sqrt(1-((0.6 c)/c)^(2))`
`=m_(0)/sqrt(1-0.36)=m_(0)/sqrt(0.64)=m_(0)/0.8`
`m=1.25 m_(0)`
% increase in mass `=((m-m_(0))/m_(0))xx100`
`=((1-25 m_(0)-m_(0))/m_(0))xx100`
`=25 %`