A flywheel initially rotating at 120 rpm retards and its angular speed reduces to 10 rpm. If the retardation in uniform and time taken is 1.5 s, then calculate the numberr of rotations made before coming to a soap.

Explanation

Given `omega_r=10rpm=120xx2xx3.142//60=12.568rads`
t=1.5s
Using `prop=(omega_r-omega_i)/t=(1.043-12.5689)/(1.5)`
i.e `prop=-7.683rads^(-2)`
Applying `theta=omega_1t+1/2propt^2`
We get `theta=12.568xx1.5+1/2(-7.683)xx(1.5)^2`
i.e `theta=18.852-8.643`
`theta=18.852-8.643`
`theta=10.209rad`
Number of rotations=`(10.209_/(2pi)=(10.209)/(2xx3.142)=1.62`