Question

A runner completes one round of a circular path of radius r in 40 seconds. his displacement after 2 minutes 20 seconds will be -

Answer 1

2 x Radius

Given:

Time Taken by the runner to complete one round = 40 seconds

Displacement time = 2 min 40 secs

Converting into seconds:

= 2 x 60 + 40

= 120 + 20

= 140 seconds

We can write it as:

= 3 x 40 + 20

Here 3 x 40 indicates 3 cycles and 20 indicates half a cycle

Calculating the runners displacement:

The displacement of the runner will be equal to the diameter of the tracks

So,

Displacement = 2 x Radius

Also we can calculate the distance the runner covered:

= Circumference of the track x 3 + Circumference of Half Cycle

= 2 x pi x r x 3 + pi x r

= 6 x pi x r + pi x r

= 6πr + πr

= 7πr

Therefore, the distance covered by his is 7πr Meter.