Question

Please tell the answer with full explanation

Answer 1

Potential energy to lift the load = (40 N) x (0.5 m) = 20 joules.

Usable power from the motor = (0.2) of (40 W) = 8 W = 8 joules per sec.

-- You need 20 joules to do the job.

-- You're getting 8 joules per sec from the motor.

-- At that rate, it'll take (20/8) = 2.5 sec to do the job.   (choice-B)