Question

The work done by a particle moving with a velocity of $0.7\, c$ (where $c$ is the velocity of light) in empty space free of electromagnetic field and far away from all matter is :

• A. positive
• B. negative
• C. zero
• D. infinite

Answer 1

Answer: (C)

zero

Answer 2

Acceleration of the particle
$a=\frac{d v}{d t}=\frac{d}{d t}(0.7 c)=0$
$(\because c=$ Constant$)$
Force on the particle
$F=m a=0$
Thus, work done by a particle will be zero.