Q128 / 160 · AP EAMCET 2021 (19 Aug Shift 2) · Physics

A quarter horse power motor runs at a speed of $600 rpm .$ Assuming $60 %$ efficiency, the work done by the motor in one rotation is

Solution

Given, the power, $P = \frac{1}{4} hp = \frac{746}{4} = 186.5 W$

Effective power $\Rightarrow P' = 186.6 \times \frac{60}{100} = 111.9 W$

Angular velocity, $ω = \frac{2 π \times 600}{60} = 20 π$

Work done in one rotation $= \frac{111.9 \times 2 π}{20 π} = 11.19 J$

Hence, the correct answer is option: 'D'.