A scuba instructor is preparing newly certified divers for their first open-water descent
PHYSICS · Multi-part · CBSE · Physics · Mechanical Properties of Fluids · Mechanical Properties of Fluids
Problem
A scuba instructor is preparing newly certified divers for their first open-water descent. Before entering the water, each diver checks the pressure gauge attached to the air cylinder. The gauge reads zero while the tank valve is still closed and the cylinder is exposed only to the surrounding air at standard sea-level conditions.
Answer the following questions about the nature of pressure readings and their significance for the divers’ safety.
(a) Describe the distinction between gauge pressure and absolute pressure, making explicit reference to the role of atmospheric pressure at sea level.
(b) Explain why the mechanical pressure gauge on the tank reads zero when the cylinder valve is closed, even though the air inside the cylinder is at the same pressure as the surrounding atmosphere.
(c) A diver later descends to a depth where the ambient water pressure is noticeably higher than at the surface. Explain why dive computers that calculate forces on the diver’s equipment must use absolute pressure instead of gauge pressure when determining the net force on the faceplate of the diver’s mask.