High School Physics

Liquid Pressure

In this post, we will discuss Liquid Pressure and related topics.

What is liquid pressure | What is liquid pressure for class 8

Liquid pressure is the pressure exerted by Liquids on their container and on any object in the liquid inside the container.

Properties of liquid pressure | Laws of liquid pressure

Liquid pressure:

  • acts in all directions
  • increases with depth
  • increases with the density of the liquid

Liquid pressure formula derivation

Let’s derive a formula for the pressure P at a depth h in a liquid of density ρ.

Liquid pressure formula derivation

Consider a frame with an area A in the liquid (figure 1). The liquid within this frame is in equilibrium with the liquid outside it. The liquid inside the frame has a volume of A × h and a mass of ρ × A × h.

The weight of the liquid is therefore g ×ρAh (where g is the acceleration due to gravity).

The weight of this liquid acts downwards on the liquid below it; this is the force in the equation that defines pressure.

The pressure p at the depth h in the liquid is, therefore, P = ρAgh/A = ρgh

Liquid pressure formula

Pressure P at a depth of h in a liquid of density ρ is expressed with the following formula:
P = ρgh

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