Question

An athlete completes one round of a circular track of radius $R$ in $30$ sec. What will be the magnitude of displacement at the end of $2$ min $30$ sec?

• A. $\text{Zero}$
• B. $R$
• C. $2R$
• D. $2\pi R$

Answer 1

The correct option is A $\text{Zero}$

Total time of motion is $2$ min $30$ sec = $150$ sec
Time period of circular motion = $30$ sec
In $150$ sec athlete will complete$=\frac{2\pi R}{30}\times 150=5\left(2\pi R\right)=5\text{revolutions}$
So, he will be at the starting point i.e. Displacement is zero.