Physics – 1.8 Pressure | e-Consult

The pressure beneath the surface of a liquid increases with depth. This is because the pressure is due to the weight of the liquid above. Consider a point within the liquid; it is acted upon by gravitational forces from all the liquid above it. The deeper the point, the more layers of liquid are above, and therefore the greater the total weight and the resulting pressure.

We can think of this as the force exerted by the liquid per unit area. The force due to gravity is proportional to the mass of the liquid above. Since the depth is directly related to the mass of the liquid above, and the area of the surface is constant, the pressure increases linearly with depth. The pressure at the surface is atmospheric pressure, which is the pressure exerted by the air above the liquid. As depth increases, the atmospheric pressure is added to the weight of the liquid above, resulting in a greater overall pressure.