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Class 11
Physics :-NCERT Solutions - SYSTEM OF PARTICLES AND ROTATIONAL MOTION

Page No 179:
Question 7.15:
To maintain a rotor at a uniform angular speed of 200 rad 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:

Angular speed of the rotor, ω = 200 rad/s

Torque required, τ = 180 Nm

The power of the rotor (P) is related to torque and angular speed by the relation:

P = τω

= 180 × 200 = 36 × 103

= 36 kW

Hence, the power required by the engine is 36 kW.


SET

NCERT Physics Class 11