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)?