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# Hydrostatic Pressure Formula and Sample Problems

## What is Hydrostatic Pressure?

Pressure is commonly defined as force per unit area. But in liquids, the column of liquid exerts a constant force downward due to its weight. The pressure exerted by a column of liquid is called hydrostatic pressure.

This force due to the liquid's weight can be computed using the liquid's density and height. This is the reason why hydrostatic pressure has a different formula than pressure in solids.

## Hydrostatic Pressure Formula

Hydrostatic pressure can be computed by multiplying the density of the fluid by the acceleration due to gravity and the depth. In symbols,

P = pgh

where P is the hydrostatic pressure, p (rho) is the density of the liquid, g is the acceleration due to gravity and h is the height from the surface or the depth.

## Hydrostatic Formula in Action

How much is the hydrostatic pressure experienced by a scuba diver at 30 meters below the surface of the ocean?

To solve this problem, we have to enumerate the given. But the only given is the height from the surface or the depth which is 30 meters.

The rho or the density of the fluid must be also given or we can rely with our previous knowledge that the density of seawater is 1,030 kilograms per cubic meters.

The acceleration due to gravity is of course 9.8 meters per second squared.

Now, let's solve the problem.

P = pgh Hydrostatic Pressure Formula

P = (1,030 kg/m^3)(9.8 m/s^2)(30 m) Substitution

P = 302,820 Pascals Multiplication

Therefore, the hydrostatic pressure at 30 meters below the surface of the ocean is 302,820 Pascals.

## Your Turn: Solve these hydrostatic pressure problems

For each question, choose the best answer. The answer key is below.

1. How much is the hydrostatic pressure experienced by a diver at 25 meters below the surface of the ocean?
• 252,530 Pascals
• 252,350 Pascals
• 252,035 Pascals
2. What is the hydrostatic pressure at the bottom of a 100 meter deep freshwater lake?
• 1,009,400 Pascals
• 1,005,000 Pascals
• 980,000 Pascals

1. 252,350 Pascals
2. 980,000 Pascals

first timer on October 27, 2014:

new at this game would have enjoyed more problems to solve great spread

Daniel Gubalane (author) from Ormoc City on February 03, 2013:

Thank you AverageWriter1! This is my first hub and I'm looking forward to creating more tutorials here on hubpages.

AverageWriter1 from California on February 02, 2013:

Well written hub. Very informative, I enjoyed reading it and taking the quiz at the end.