Pressure The result of a force distributed over a given area.

Equation for Pressure:

Pressure = Force / Area

Force = Newton’s Area = m2

Units for pressure = Pascal (Pa)

Example #1 Each tile on the bottom of a swimming pool has an area of 0.50 m2. The water above each tile exerts a force of 11,000 N on each tile. How much pressure does the water exert on each tile?

Pressure = Force / Area Pressure = 11,000 N / 0.50 m2

Pressure = 22,000 Pascal's

Example #2 The weight of a gallon of milk is about 38 N. If you pour 3 gallons of milk into a container whose bottom has an area of 0.60 m2, how much pressure will the milk exert on the bottom of the container?

Pressure = Force / Area Pressure = (38 N * 3) / 0.60 m2

Pressure = 114 N / 0.60 m2

Pressure = 190 Pascal's

Two factors that affect fluid pressure:

1.  Depth 2.  Type of fluid

Air Pressure and the Atmosphere

Air pressure decreases as the altitude increases.

Examples:

•  Ears popping while on a plane •  Ears popping while diving deep in a swimming pool

Pascal’s Principle

A change in pressure at any point in a fluid is transmitted equally and unchanged in all directions throughout the fluid.

What is a hydraulic system?

A device that uses pressurized fluid acting on pistons of different sizes to change a force.

How does a hydraulic system use fluid pressure to do work?

An increased output force is produced because a constant pressure is exerted on the larger area of the output piston.

Example

Draw this diagram:

5,000 N

Bernoulli’s Principle

As the speed of a fluid increases, the pressure within the fluid decreases.

Air always moves from higher pressure to lower pressure

How do we use Bernoulli’s principle to make planes fly (Draw diagram)?