Question

A solid disk with a radius of `24 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

`tau~~4.2` `N` `m`

Explanation:

One way to express torque is by the equation `tau=P/omega`. This is rearranged from `P=tauomega`.

Given that `P=480W` and `f=18Hz`, we can determine the angular velocity `omega` and use this to calculate the torque.

`omega=2pif=2pi(18s^-1)=36pi(rad)/s`

So, we have:

`tau=(480W)/(36pi(rad)/s)~~4.2` `N` `m`