What is lateral pressure?

Lateral pressure refers to the pressure exerted by a fluid in a direction that is perpendicular (sideways) to the direction of gravity. In simpler terms, while we often think of pressure as acting vertically downward due to the weight of a fluid, fluids actually exert pressure equally in all directions — upward, downward, and sideways. This sideways pressure is called lateral pressure.

The concept arises from Pascal’s Law, which states that pressure applied at any point in a confined fluid is transmitted equally in all directions. Thus, when a fluid is at rest, its molecules move randomly and exert forces on the walls of the container in every direction. As a result, the walls experience a uniform lateral push.

A classic example is observed in dams and water tanks. The walls must be built thick and strong at the bottom because lateral pressure increases with depth — the deeper the fluid, the greater the pressure exerted sideways. Similarly, when a hole is made in the side of a water-filled container, water jets out due to lateral pressure.

In conclusion, lateral pressure is a fundamental property of fluids, ensuring that they exert pressure not just vertically but equally in all possible directions.