Question

The rate of rotation of a solid disk with a radius of `4 m` and mass of `5 kg` constantly changes from `16 Hz` to `5 Hz`. If the change in rotational frequency occurs over `7 s`, what torque was applied to the disk?

Answer 1

The torque is `=237kgm^2s^(-1)`

Explanation:

The torque is `tau=Ialpha`

`tau=I(domega)/dt`

The moment of inertia of a solid disc `I=(mr^2)/2`

`I=3*4^2/2=3*8=24 kg m^2`

`(domega)/dt=(16-5)/7*2pi=(22/7pi )rads^(-1)`

So, the torque is

`tau=24*22/7pi=237kgm^2s^(-1)`