Question

An Athlete completes one round of a circular track of diameter 200 m in 40s. What will be the distance covered and the displacement at the end of 2m and 20s?

Answer 1

Given,
diameter = 200 m
time taken to complete one round = 40s

we know, displacement will be zero when athlete completes one round.
so, every 40 sec displacement equals zero.
we have to find distance and displacement at the end of 2min and 20 sec .
time = 2 × 60 + 20 = 140 sec
here, time = (3 × 40 + 20 ) sec ,To see time it is clear that athlete completes three and half round . so, displacement due to three round equals zero. and half round = diameter of circular path = 40m

hence, displacement at the end of 2min and 20sec = 40m

and distance = 3 × πd + πd/2
= 3π × 40 + π × 40/2
= 120π + 20π
= 140π m
= 140 × 22/7 m = 440m

hence, distance covered by athlete = 440m

Answer 2

$\bold{HEY!!}$

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⏩An athlete takes 40 sec for 200 m diameter circular track. in 40 sec.

⏩He covers 2 pi R distance (2R = 200 m) then the athlete moves for 2 min 20 sec which is 140 sec. so, in 140 sec he moves {2 pi R)/40}×140 = 7 pi R 

⏺️d = 7 pi R 

⏺️7×(22/7)×100

⏺️2200m

⏩Displacement = shortest path travelled by any object. 

⏩So after 7 pi R it'll be at point diametrically opposite point of its initial position. 

⏩⏩Then displacement = 2R =200m.