Question

If the boy takes 20 sec to complete one round then what will be the speed(in m/s) of that boy​

Answer 1

Answer:

The diameter of the circular track is given as 200 m. That is, 2r=200 m.

From this radius is calculated as Radius, r = 100 m.

In 40 sec the athlete complete one round. So, in 2 mins and 20 secs, that is, 140 sec the athlete will complete = 140 / 40 = 3.5 (three and a half) rounds.

One round is considered as the circumference of the circular track.

The distance covered in 140 sec = 2πr×3.5=2×3.14×100×3.5=2200 m.

For each complete round the displacement is zero. Therefore for 3 complete rounds, the displacement will be zero.

At the end of his motion, the athlete will be in the diametrically opposite position. That is, displacement = diameter = 200 m.

Hence, the distance covered is 2200 m and the displacement is 200 m.

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Answer 2

Answer:

Time taken = 20 seconds

to complete one round means, we have to find the circumference

d= 30m , r= 15m [30/2]

v= 2πr/t

= 2 × 22/7 × 15 × 20

= 4.7m/s

Hope this helps!

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