Question

An athlete completes one round of a circular track of diameter 200 m in 40 s. If he continues to run, what will be the distance covered and the displacement at the end of 2 minutes 20 s respectively ? (1) 2200m , 200m (2) 2200m, 0m (3) 4400m, 400m (4) 2200m, 400m

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Answer 1

Let us assume that an athlete starts from point A to point B. Here it covers half of the revolution. If he return backs to it's initial point i.e. A then it covers the one complete revolution.

Given that, an athlete completes one round of a circular track of diameter 200 m in 40 s.

Distance covered in one round = Circumference of circle.

{ Circumference of circle = 2πr }

So,

Distance covered in one round = 2πr

(diameter is 200 m so radius is 100 m)

= 2 × 22/7 × 100 = 4400/7

Now,

Speed = Distance/Time

= (4400/7)/40 = 4400/(7 × 40)

We have to find the distance covered and the displacement at the end of 2 minutes 20 s respectively.

2 min 20 sec = 2*60 + 20 = 140 sec

So, distance covered at the end of 140 sec = 4400/(7 × 40) × 140

= 2200 m

Displacement is defined as the shortest distance between the initial and final points.

So, Displacement of an athlete completes one round of a circular track is equal to it's diameter of circular track.

Displacement of an athlete is 200 m.