Question

An athlete complete one round of a circular track of radius R in 40 seconds .What will be his displacement at the end of 2 minutes 20 second ?​

Answer 1

it will be πR

Explanation:

because after 2min he will complete 4th cycle means dislplacement 0 and in next 20 sec he will complete hal cycle

Answer 2

Explanation:

The athlete completes a distance of 2πR m in 40s,(since 2πR is the circumference of the track) he will cover 3.5×2πR metres in 140s (using unitary method). Therefore he finishes 3 and a half rounds of the track in 140 seconds.

Hence his distance covered 7πR metres.

m2−n2

Since displacement is the shortest distance between the starting point and finishing point, 3 rounds provide zero displacement, as he returns to the same point every time he finishes one round. So his net displacement is only accounts for the final half-round and is 1/2 × 2πR = πR metres

other

In 40s ,one round is completed = 2.22/7.r

2 min 20 s =140 sec..

In 120 sec it'll be back to its original postion ....(40×3)

And the next 20 sec.it will cover half the distance....(40/2)

:. The displacement would be its diameter...that is 2R.