Question

A body of mass $m$ is moving in a circle of radius $r$ with a constant speed $v$. The force on the body is $\frac{m{v}^2}{r}$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle?

• A. $\frac{m{v}^2}{\pi r^2}$
• B. Zero
• C. $\frac{m{v}^2}{r^2}$
• D. $\frac{\pi r^2}{m{v}^2}$

Answer 1

The correct option is B Zero

Work done by centripetal force is always zero, because force and instantaneous displacement are always perpendicular.
$W=\overrightarrow{F}.\overrightarrow{s}=Fs\cos \left({90}^{\circ }\right)=0$