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 UshaNCERT Class IXSciences - Main Course BookChapter 8. Motion

Answer 1

Length of the pool: 90m
Average speed:
Speed= Distance/Time
speed=180/60
speed=30 m/s
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velocity=displacement/time
displacement=0( Since she comes back to the same place)
velocity=0

Answer 2

Average speed:
Time taken= 1 min= 60 sec
Total Distance cover =180m
Average speed = total distance cover÷total time taken
=180÷60=3m/s

Average velocity :
Total displacement =0
Time taken= 60 sec(1 min=60 sec)
Average velocity= total displacement ÷total time taken
=0÷60=0 m/s