Question

How to find velocity of a rotating object from frequency?

Answer 1

◆ ∆nswer ◆

Simple :. we know , v = w × r

where ,

v = velocity
w = angular velocity
r = radius of rotation..

now , f = frequency = 1/ Time period = w/2π

as , w = 2π/T

so , v = 2πfr

#Superman

Answer 2

There are many ways to find the frequency in uniform circular motion depending on what is given to you in the problem.

First, be clear that there is a difference between the "frequency", f, and the angular frequency, ω , but they are related through this:
2π⋅f=ω

We also know that the period, T, is related to f through T=1f

If the speed is known then you can use:
v=2πrT=2πrf ⇒f=v2πr
This equation comes from knowing the distance travelled for one complete revolution is 2πr and the time taken is T.

Example problem: If a ball takes 20 seconds to make 5 full revolutions, find its period, frequency, and angular frequency.

The period is the time it take for ONE revolution, so 
T=20s5=4s

The frequency is then f=1T=14s=.25s=.25s−1=.25Hz

The angular freq is then ω=2π⋅0.25Hz=1.57rads