1. - Pressure
Area
The area of a surface is the number of square units that it covers. To find the area of a rectangle, multiply its length by its width. The area of the rectangle below is 2 cm X 3 cm, or 6 cm2.

2. What Is Pressure? - Pressure
Pressure decreases as the area over which a force is distributed increases.

3. Pressure = Force Area Units Force Newtons (N) Area Meters squared (m2)
Pressure N = Pascal (Pa) m2

4. Fluid Pressure - Pressure
All of the forces exerted by the individual particles in a fluid combine to make up the pressure exerted by the fluid.

5. Variations in Fluid Pressure
As your elevation increases, atmospheric pressure decreases.

6. Variations in Fluid Pressure
Water pressure increases as depth increases.

7. Previewing Visuals - Pressure
Before you read, preview Figure 5. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
Pressure Variations
Q. Why does the pressure change with elevation and depth?
A. Air and water exert pressure, so pressure varies depending on how much air or water is above you.
Q. How much greater is water pressure at a depth of 6,500 m than it is at sea level?
A. It is about 650 times greater.

8. Buoyancy - Floating and Sinking
The pressure on the bottom of a submerged object is greater than the pressure on the top. The result is a net force in the upward direction.

9. Buoyancy - Floating and Sinking
The buoyant force acts in the direction opposite to the force of gravity, so it makes an object feel lighter.

10. Buoyancy - Floating and Sinking
Achimedes’ principle states that the buoyant force acting on a submerged object is equal to the weight of the fluid the object displaces.

11. Buoyancy - Floating and Sinking
A solid block of steel sinks when placed in water. A steel ship with the same weight floats.

12. Density - Floating and Sinking
Changes in density cause a submarine to dive, rise, or float.

13. Relating Cause and Effect
- Floating and Sinking
Relating Cause and Effect
As you read, identify the reasons why an object sinks. Write them down in a graphic organizer like the one below.
Causes
Weight is greater than buoyant force.
Effect
Object is denser than fluid.
Object sinks.
Object takes on mass and becomes denser than fluid.
Object is compressed and becomes denser than fluid.

14. Pressure
P = F N A m2 Pascal’s Principal Pressure applied to a fluid in a closed container is transmitted equally to every point of the fluid and to the walls of the container.

15. Hydraulic Lift
P1 =P2
Therefore:
F1 = F2
A A2
F2, A2
F1, A1

16. How Airplanes Wings Work

17. Click the Video button to watch a movie about density.
- Floating and Sinking
Density
Click the Video button to watch a movie about density.

18. Bernoulli Principle: States that as the speed of a moving fluid increases, the pressure within the fluid decreases

19. Bernoulli’s Principle is what allows birds and planes to fly.
The secret behind flight is ‘under the wings.’

20. AIRFOIL On top: greater air speed and less air pressure
On bottom: less air speed and
more air pressure

21. LIFT
THRUST
DRAG
GRAVITY

22. less air speed more pressure greater air speed less pressure
Spoiler – airfoil reversed
less air speed
more pressure
greater air speed
less pressure
net force: downward

23. Racecar less air speed more pressure greater air speed less pressure
Spoiler provides better
Traction and avoids lift
greater air speed
less pressure
net force: downward

24. slow air speed
fast air speed

25. Curve Ball

26. Atomizer – As air passes at top of tube,
the pressure decreases and fluid is drawn up
the tube.