Question

A U-Shaped tube of constant cross-sectional area contains water of density 1000kg/m cubed. Bothe side of the tube are open to the atmosphere. The atmospheric pressure is 1. 00 x 10 to the power of 5. The left hand side is now connected to a gas supply using a length of rubber tubing. This causes the level of the water in the left hand side to drop by 0. 200m. Calculate the pressure of the gas supply. Give your answer to 3 significant figures

Answer 1

If the water in the left side drops .2 m then the water on the right side rises by .2 m

The pressure on the gas is due to the height difference of the water on the two sides.

P = ρ g h

ρ g = 9.8 m/s^2 * 1000 kg / m^3 = 9800 N/m^3 weight density of water

P = 9800 N/m^3 * .4 m = 3920 N / m^2 = 3.92E3 N/m^2

Absolute pressure of gas = 3.92E3 / 1.01E5 = .0388 atmosphere