Question

An athlete finishes a round circular track of radius $R$ in $40\text{s}$. What is the displacement at the end of $2\text{minutes 20 s}$?

• A. $\text{2R}$
• B. $\text{2πR}$
• C. $\text{7πR}$
• D. Zero

Answer 1

The correct option is A $\text{2R}$

Given:

$T=40\text{s}$
$t=2\text{minutes 20 sec}=2\times 60+20=140\text{s}$


Assuming that the athlete starts the motion from point $A$.

After $140\text{s}$, he will complete $3$ and half rounds.

Therefore, after $\text{2 minutes and 20 sec}$, the athlete will be at point $B$.

So, the displacement of athlete is,

$\text{d = AB =2R}$

Hence, option $\left(A\right)$ is the correct answer.