Question

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

Answer 1

boy covers 60 m distance with velocity 20m/s and 40m next distance with velocity 10 m/s .

we know,
time = distance/speed or displacement /velocity
boy takes time to cover 60 m distance = 60/20 = 3 sec
again, takes time to cover next 40 m distance = 40/10 = 4 sec


now, average velocity = total displacement/total time taken
= 100 m/(3 sec + 4sec)
= 100/7 m/s
= 14.28 m/s

Answer 2

Given,
A boy swims in a 100 m long pool. He covers 60 m with a velocity of 20 m/s and covers the rest of the distance with a velocity of 10 m/s.

We know,
Speed = distance/time

Then,

Time = distance/speed  

So,
Time taken by boy to cover 60 m distance:
= 60/20
= 3 seconds 
And, Time taken  to cover next 40 m distance:
= 40/10
= 4 seconds 


We know,

Average velocity = total displacement/total time taken 
here,
Total distance = 100m
Total time = 3+4 seconds = 7 seconds

So Avg. Velocity
= 100/7 m/s 
= 14.28 m/s

Hope It Helps You!