Question

A child moves around the circumference of a merry-go-round and completes a round in 5 seconds. How much time will it take for him to travel along the diameter and come back?

• A. 10 seconds
• B. 3.18 seconds
• C. 5.26 seconds
• D. 6.36 seconds

Answer 1

The correct option is B

3.18 seconds

Take radius of the circle to be r.

First case, distance travelled = 2$\pi$r.

Second case, distance travelled will be 4r.

As speed is constant. So, time taken will be proportional to distance travelled.

T = $\left(\frac{4r}{2\pi r}\right)\times 5=\frac{2}{\pi }\times 5$ = 3.18 seconds.