# A solid disk with a radius of 3 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 4 Hz?

Mar 17, 2017

The torque is $= 19.1 N m$

#### Explanation:

mass of disc $= 12 k g$

radius of disc $= 3 m$

The power is related to the torque by the equation

$P = \tau \cdot \omega$

$P = 480 W$

angular velocity, $\omega = 4 \cdot 2 \pi r a {\mathrm{ds}}^{-} 1$

torque, $\tau = \frac{P}{\omega}$

$= \frac{480}{8 \pi} = \frac{60}{\pi} = 19.1 N m$