To maintain a rotor at a uniform angular speed of 100 `rads^(-1)` an engine needs to transmit a torque of 200 Nm. What is the power required by engine ? Assume 100 % efficiency of engine.

Explanation

Work done by torque in turning rotor by an angle `d theta` is `=tau d theta` So, power delivered by engine,
`P=("Work done")/("Time taken")=tau(d theta)/(dt)`(dt= taken for turning by angle `d theta`)
or `P = tau omega`
So, power required `= 100 xx 200 = 20000 W`
`=20 kW[because 1kW=1000]`.