Question

Calculate the useful power output for an electric motor that uses 200 W and has an

efficiency of 40%

Answer 1

Correct option is B)

Power with which crane lifts the load =0.8×0.9 × input power

P=0.8×0.9×200 kW

Now, P=

F

.

v

Here, F=mg (since there is no acceleration)

10

3

×0.8×0.9×200=3.6×10

3

×10×v

⇒v=4 m/s