Question

A 10kg block is attached to a light cord that is wrapped around the pulley of an electric motor. What is the power output of the motor..?
when it is pulling the block upward with an instantaneous speed of 3m/s and an upward acceleration of 2 m/s?

a)300W b)360 c)600 d)240 e)480

Answer 1

Answer:

Option B is correct.

Power = 360 W

Explanation:

Power = Work done/time

Work done = Force × distance moved through by the force

Power = Force × (distance moved through by the force/time)

(Distance moved through by the force/time) = velocity = 3 m/s

Power = Force × velocity

Force = ma

But the acceleration in this case is this acceleration + acceleration due to gravity because the force has to be overcoming the force of gravity to now move the object upward at 2 m/s²

a = (2 + g) (assume acceleration due to gravity = 10 m/s²

a = 2 + 10 = 12 m/s²

F = ma = 10 × 12 = 120 N

Power = F × v = 120 × 3 = 360 W