An air pump is pumping air in to a large vessel against a pressure of 1 atmosphere. In each stroke 1000CC of air enters in to the vessel. If the number of strokes made by the pump per minute is 30, the power of the pump is (1 atm =${{10}^5}^{ }$Pa)

Discharge = Volume flow rate

$Q=\left(1000\times {10}^{-6}\right)\times \frac{30}{60}{m}^3/s$=$5\times {10}^{-4}$

If A be the effective area of flow, v be the average velocity of air and p be the pressure in the vessel, then resistive force F = p x A
Power = F x v =(pA) x v =p x Q = ${10}^5\times 5\times {10}^{-4}$= 50 Watt.