Question

A boy observed a circular track with radius $r$ and completed one revolution of the track. Choose the correct statement(s).

• A. Non- zero
• B. Zero
• C. 4 J
• D. Can't be said

Answer 1

Answer: (A), (B)

The correct options are
A

Non- zero

B

Zero

Since the boy completed one circle on the track, his final and initial positions are the same. Hence, his displacement is zero.

$\text{Average velocity}=\frac{\text{Displacement}}{\text{Time taken}}$
Displacement is zero so average velocity is also zero.

Distance travelled is the perimeter of the track i.e., $2\pi r$.
$\text{Average speed}=\frac{\text{Distance}}{\text{Time taken}}$
or, $\text{Average speed}=\frac{2\pi r}{\text{Time taken}}$
Hence, average speed is non-zero.