1. Pressure Pressure is a force exerted over an area on the surface
of an object.
Force and Pressure are not the same thing:
Pressure decreases as the area over which a force
is applied increases.
Pressure less
Force
Force
Pressure
greater

2. Pressure = Force Area Units of pressure are Newtons/meter2
1 N/m2 = 1 pascal (Pa)

3. Pascal's Principle
Force
Force
When a force is applied to a confined fluid, the change
in pressure is transmitted equally to all parts of the fluid.

4. Cartesian Diver
Pressure increased
Pressure decreased

5. Pressure is caused by the movement of particles
in the fluid. Every time they bump against the side
of the container they create pressure. The more bumps
the more pressure.
Fluid Particles

6. The more particles, the more pressure. The
faster the particles move, the more pressure.
Fluid Particles

7. Air Pressure Water Pressure
Pressure caused by the weight of the air in the atmosphere
as gravity pulls it down toward the center of the earth.
Water Pressure
Pressure caused by the weight of water as gravity pulls it
down toward the center of the earth.
Remember, weight is a force.

8. Balanced Pressure
Air and water pressures press on objects from every direction.

9. If the pressure becomes unbalanced, the pressure of air
or water can crush an object.
The air pressure inside balances the
air pressure outside the container.
But if we take the air out of the
container, the outside pressure
will be far greater than inside and
crush the can.

10. Atmospheric Pressure and Elevation
As your elevation increases, atmospheric pressure decreases.
Water Pressure and Depth
Water pressure increases as depth increases.

11. Buoyancy The force in liquids that acts opposite to gravity—it
causes objects to feel lighter.
Objects sink if their weight is greater than the buoyant
force acting on them.

12. Archimedes' Principle The buoyant force acting on a
submerged object is equal to
the weight of the fluid the
object displaces.

13. Archimedes' Principle The buoyant force acting on the object
equals the weight of
the water displaced
by the object.

14. Weight
Weight
Buoyant Force
Buoyant Force

15. DENSITY Density = Mass Volume
If the density of an object is less than the density of water,
the object will float.
If the density of an object is greater than the density of water,
the object will sink.

16. Pascal's Principle
Force
Force
When a force is applied to a confined fluid, the change
in pressure is transmitted equally to all parts of the fluid.

17. Hydraulic Systems Pressure of 10N/m2 Force = 10N/m2 x 10m2 100N Force
10m2 area
1m2 area
Pressure = 10N
1m2
Pressure of 10N/m2

18. Pressure Force Area ? 300N 20m2 15N/m2 15m2 3,000N/m2 150N 750N 7.5m2
How much pressure is produced by a 150N force acting
over an area of 3m2?
A 5N force is applied to a 5m2 piston in a hydraulic device.
If the second piston has an area of 25m2, what is the force
produced by this second piston?
Pressure
Force
Area ?
300N
20m2
15N/m2
15m2
3,000N/m2
150N
750N
7.5m2

19. Bernoulli's Principle so... The faster a fluid moves
the less pressure the fluid exerts.
so...
As the speed of a moving fluid increases,
the pressure within the fluid decreases.

20. Moving stream of wind (fluid) Smoke moves up chimney from high to
Lower Pressure
Moving stream
of wind (fluid)
Smoke moves up
chimney from high to
low pressure.

21. Wings are shaped so that air moves
faster over the top of the wing than
under the wing. This causes lower pressure
above the wing than below and creates lift so the plane can fly.