Question

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

Answer 1

In 40 secs-->1 round..
In 2 mins 20 secs=140 secs
No. Of rounds=140/40=3½
Therefore the runner would reach the diametrically opposite point..
=> displacement = diameter
=2r

Answer 2

Answer:

His displacement after 2 minutes 20 seconds will be 2 r.

Explanation:

Given that,

Radius of the circle = r

We need to calculate the displacement,

A runner completes one round of a circular path of radius r in 40 second.

A runner completes 3.5 round in 140 second.

So, the displacement will be zero in 3 round.

In 0.5 round, the runner covers the distance is 2 r.

Therefore, The displacement will be

Displacement = final position - initial position

$D = 2r-0$

$D = 2r$

Hence, His displacement after 2 minutes 20 seconds will be 2 r.