A student wishes to find the velocity of air flowing through a pipe. He has a pressure gauge which displays only the dynamic pressure. The pressure gauge reads 0.018 mm Hg. Assume density of air to be 1.225 kg/m3, find the velocity V of air (ρHg = 13600 kg/m3).

Correct Answer: 2 m/s
(0.018 mm Hg * 13.6 * 9.8) = 2.4 bar. Dynamic pressure is given by ρV2/2. Equating 2.4 bar with dynamic pressure gives V = 2 m/s.