A diver is swimming in the sea at a depth of 20 m. She breathes out an air bubble. The bubble rises to the surface.
Atmospheric pressure at the surface of the sea = 1.0 × 105 Pa
Density of sea water = 1030 kg/m3
Gravitational field strength g=10 N/kgg = 10\ \text{N/kg}g=10 N/kg
Calculate the pressure due to the sea water at a depth of 20 m.
Use the equation: pressure due to a column of liquid=height of column×density of liquid×g\text{pressure due to a column of liquid} = \text{height of column} \times \text{density of liquid} \times gpressure due to a column of liquid=height of column×density of liquid×g
Show that the total pressure on the bubble at a depth of 20 m is about 3 × 105 Pa.
The volume of the bubble at a depth of 20 m is 4.0 cm3.
Assume that the temperature of the air in the bubble does not change.
Use the equation: pressure×volume=constant\text{pressure} \times \text{volume} = \text{constant}pressure×volume=constant
Calculate the volume of the bubble when it reaches the surface.
Divers are told never to hold their breath as they swim up to the surface.
Explain why.
50 exam-style questions on OCR GCSE Physics 1.3 Pressure, covering 1.3.1 Molecular motion, temperature and gas pressure, 1.3.2 Gas pressure at constant volume, 1.3.3 Compressing and expanding gases, 1.3.4 Gas volume and pressure at constant temperature, 1.3.5 Doing work on a gas, 1.3.6 The Earth's atmosphere and atmospheric pressure, 1.3.7 Atmospheric pressure and height, 1.3.8 Floating and sinking, 1.3.9 Pressure in liquids and upthrust, and 1.3.10 Pressure differences with depth. Each one has a worked solution and a mark scheme showing where the marks go.