Question

A solid disk with a radius of `21 m` and mass of `8 kg` is rotating on a frictionless surface. If `480 W` of power is used to increase the disk's rate of rotation, what torque is applied when the disk is rotating at `18 Hz`?

Answer 1

The torque is `=4.24Nm`

Explanation:

mass of disc `=8kg`

radius of disc `=21m`

The power is related to the torque by the equation

`P=tau *omega`

`P=480W`

Frequency of rotation is `f=18Hz`

`omega=f*2pi`

angular velocity, `omega=18*2pi rads^-1`

torque, `tau=P/omega`

`=480/(36pi)=4.24Nm`