- The Effect of Pressure on the Diver

The Effect of Pressure on the Diver

The effect of pressure on solids, liquids and gas:

As opposed to liquids and solids, gas is compressible. Changes in pressure, therefore, affect density of gases only, and not density of liquids or solids. If one exerts pressure on a liquid, no changes will occur to its density and volume. Pressure within a liquid grows without causing changes in volume. The volume and density of gas, however, is affected directly by pressure. If one doubles the pressure on a certain amount of gas (from 1 ATM to 2 ATM), the volume of the gas will become half of its original volume. If the pressure is tripled, the volume will become a third of its original volume. Now, if one lowers the pressure by 3, the volume will grow by 3 and return to its original
volume.

Boyle-Marriott Law:

Determines that a change of pressure (P) will cause a change of volume (V) in a certain amount of gas, inversely proportioned.
Simply put, the more the pressure grows, the smaller the volume is, and vice versa.
If the pressure grows by 2, the volume grows smaller by 2.
If the pressure grows smaller by 3, the volume grows larger by 3.

To illustrate this, think of a flexible and impermeable rubber balloon that is filled with a volume of 6 liters of air. If we sink this balloon to a depth of 10 meters, we will actually be raising the outer pressure upon the balloon by 2, since at sea level the pressure is 1 ATM and at 10 meters the general pressure is 2 ATM. Since the pressure is up by 2, the volume will lessen by 2 and will become 3 liters only. The pressure within the balloon will be equal, of course, to the outer pressure, and will also be 2 ATM. If we continue and descend to a depth of 20 meters, the general pressure will then be 3 ATM, and the volume of the balloon will be 2 liters only. This is because the pressure grew from the sea level by 3, which is why the volume is 3 times smaller.