Question

An athlete completes one round of a circular track of radius R in 40 sec. What will be s displacement at the end of 2 min 20 seconds?

Answer 1

Hi.

Here is the answer---

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Time taken by the Athlete to complete one round = 40 seconds.

Thus, Number of Rounds completed in 2 minutes (120 seconds) = 120/40
   = 3 rounds.

Thus, Displacement covered by the Body in 3 rounds = 0
[Since, body returned to the same point]

Now, In remaining 20 seconds, number of rounds covered will be 20/40 round = 1/2 Round.

In One Round, Distance Covered = 2 × $\pi$ × r
                                                              = 2 × (22/7) × R
                                                              = 44R/7 


Thus, Displacement covered in (1/2) Round = (1/2)(44R/7)
                                                                       = (22/7)R
                                                                       = $\pi$ R


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Hope it helps.

Answer 2

Answer:

answer =2R

Explanation:

Time to complete one revolution =40 sec

Total time =2x60+20 = 140 sec

no. of revolution = Three and half

Therefore, displacement =2R