An Evaporative Cooling Unit Needs to Pump 100 Litres of Air

Multiple Choice

An evaporative cooling unit needs to pump 100 litres of air per second through a pipe of radius 10 cm and length 10 m. How much of a pressure difference must be applied to the air to produce this flow rate? The viscosity of air is 1.8x10-5 Pa s.

A) 4.6x10-9 Pa
B) 1.44 Pa
C) 0.46 Pa
D) 460 Pa
E) 0.057 Pa
ANS