Question

A motor is used to pump water from a depth of 5 m to fill a volume of 10 cubic meters in 5 minutes. If 50% of the power is wasted, what is the power of the motor? (Assume g = 10m/s^2)

(a) 1000/3 W

(b) 3000/3 W

(c) 5000/3 W

(d) 10000/3 W

I got this question in exam.

The doubt is from Power topic in portion Work, Energy and Power of Physics – Class 11

Answer 1

The correct answer is (d) 10000/3 W

Easy explanation: Density of water = 1000 kg/m^3

Mass of water in 10m^3 = 1000 x 10

 = 10,000 kg

Volume of water filled in 1s = 10/(5×60)

 = 1/30 m^3

Mass filled in 1s = 1/30 x 1000

 = 100/3 kg

Power = 100/3 x 10 x 5; [g = 10m/s^2]

 = 5000/3 W

Since 50% of power is wasted, power of motor = 5000/3 x 2

 = 10000/3 W.