# A solid disk with a radius of 5 m and mass of 2 kg is rotating on a frictionless surface. If 3 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?

Feb 28, 2017

The torque is $= 0.12 N m$

#### Explanation:

The power and the torque are related by the following equation

$P = \tau \omega$

Power $= 3 W$

The angular velocity $= 4 \cdot 2 \pi = 8 \pi r a {\mathrm{ds}}^{-} 1$

The torque is

$\tau = \frac{P}{\omega} = \frac{3}{8 \pi} = 0.12 N m$