Q4 of 35 Page 55

A boy swims in a 100 m long pool. He covers 60 m with a velocity of 20 ms–1 and covers the rest of the distance with a velocity of 10 ms–1. Calculate the average velocity of the boy.

To Find: Average velocity of the boy

We know,



So to find average velocity we should know


(i) Total displacement


(ii) Total time taken to travel this distance


Given


Total distance = 100m


Total time = t


Now there are two motions


Part 1


Boy covers 60 m with a velocity of 20 ms–1




Let time = t1




Part 2


Boy covers (100–60= 40m) with a velocity of 20 ms–1




Let time = t2




Total time =t








Hence


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