Question

a girl starts moving through a circular track of radius 21 m. she tooks 10 seconds to complete one rotation. find the speed &velocity after the completion of half rotation

Answer 1

Hey mate !!

Here's the answer !!

Given : Radius of circular track : 21 m

One rotation = 10 Seconds

To find : Speed and velocity in half rotation

Proof :

Circumference of a circle = 2πr

=> Circumference = 22 / 7 * 21 * 2

=> Circumference = 22 * 3 * 2 = 66 * 2 = 132 m²

Therefore speed = 66 / 10 = 66 m / sec

Velocity = 0 / 10 = 0 m / sec

Therefore at half rotation, the length = 132 / 2 = 66 m²

But in half round the speed can be assumed to be half. Hence

In half rotation Distance = 66 and Time = 5 sec.

Therefore Speed = 66 / 5 = 13.2 m / sec

Velocity = Displacement / Time

Displacement = Shortest distance which is the diameter of circle

Hence Displacement = 42 m

=> Velocity = 42 / 5 = 8.4 m / sec

Hence Speed = 13.2 m / sec and Velocity = 8.4 m / sec. ( Assumption )

Hope my answer helps !!

Cheers !!