Question

A solid disk with a radius of `9 m` and mass of `12 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 `15 Hz`?

Answer 1

The torque is `=5.09Nm`

Explanation:

mass of disc `=12kg`

radius of disc `=9m`

The power is related to the torque by the equation

`P=tau *omega`

`P=480W`

Frequency of rotation is `f=15Hz`

`omega=f*2pi`

angular velocity, `omega=15*2pi rads^-1`

torque, `tau=P/omega`

`=480/(30pi)=5.09Nm`