Question

Usha swims in a 90 m long pool. She covers 180 m in one minute by swimming from one end to the other and back along the same straight path. Find the average speed and average velocity of Usha

NCERT Class IX
Sciences - Main Course Book

Chapter 8. Motion

Answer 1

Distance = 180 m

Time = 1 min = 60sec

Average speed = total distance covered / total time taken

= 180m / 60 sec

= 3m/s

Displacement = 0m/s ( as usha come back along the same path so, the intial and final position is same )

Average velocity = displacement/ time

= 0m / 60 s

= 0m/s

Answer 2

The average speed of Usha is 3 m/sec and the average velocity is 0 m/sec.

Given,

Distance covered by Usha while swimming = 180 m

Time taken = 1 minute

To FInd,

The average speed and average velocity of Usha.

Solution,

The formula for calculating the average speed and average velocity is

Average speed = Total distance/Total time

Average velocity  = Total displacement/Total time

In this question

Total distance = 180 m

Total displacement = 0 m

Total time taken = 1 minute = 60 sec.

So,

Average speed = 180/60 = 3 m/sec

Average velocity = 0/60 = 0 m/sec

Hence, the average speed of Usha is 3 m/sec and the average velocity is 0 m/sec.