Question

2. An athlete completes one round of a circular track of radius R in 40 seconds. What will be his displacement at the end of 2 minutes 20 seconds
(a) Zero (b) 2R (c) 2πR (d) 7πR

Answer 1

As we know the displacement is the short distance between starting point to end point

So when athlete takes 40 to complete the 1 round of circular track of Radius R

Then his displacement is zero because he is at initial point after every 40 seconds

So the displacement will be 2R

(Check image)

We can solve it in this way also

Displacement after 40 sec=0

After 80 sec=0 (again back to initial point)

After 120 sec=zero

But in next 20 sec he covers half distance or we can say run over half Circumference of circular track

And at that time displacement will be diameter of that circular track or 2R


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