Question

A pump can throw up 10quintals of coal per hour from a coal mine 120m deep. Calculate the power of the engine assuming that efficiency is 80 percent.

Answer 1

Energy used in pumping = mgh
h is the height upto which coal is to be taken out.

1 quintal = 100 kg
E = 1000 ×10 ×120 = 1200000 j
power = energy/time

time = 1 hour = 3600 s

Power = 1200000/3600 = 1000/3 watt

efficiency = 80%

Power of the engine = $\frac{1000}{3}\times \frac{80}{100}=266.66watt$