Question

To maintain a rotor at a uniform angular speed of $200rad{s}^{-1}$, an engine needs to transmit a torque of 180 Nm. What is the power required by the engine?
(Note: uniform angular velocity in the absence of friction implies zero torque. In practice, applied torque is needed to counter frictional torque). Assume that the engine is 100 % efficient.

Answer 1

Angular speed of the rotor, $\omega =200rad/s$
Torque required, $\tau =180Nm$
The power of the rotor (P) is related to torque and angular speed by the relation:
$P=\tau \omega =180\times 200=36\times {10}^3=36kW$
Hence, the power required by the engine is 36 kW.