1. Unit 3 – Forces in Fluids Chapters 3 and 13 Read Pages 69 - 73

2. A fluid is a substance that assumes the shape of its container
Fluids can be a liquid or a gas

3. Kinetic Theory of Matter
Says all particles of matter are in constant motion!
Kinetic comes from the Greek word meaning “to move”
Kinetic energy is the energy of motion
This theory helps explain the behavior of liquids and gases

4. Liquids There are forces of attraction among the particles of matter
This attraction keeps the particles close together
Atoms touch but slide past one another

5. Liquids (continued) Definite (fixed) volume – it cannot be compressed
Indefinite shape – it takes the shape of the container

6. The fast moving atoms are spread out and only touch when they collide
Gases
The fast moving atoms are spread out and only touch when they collide
Particles are apart and moving so fast the attractive forces are too weak to have an effect

7. Gases (continued)
Has an indefinite shape – They will fill the container
Indefinite volume – They can be compressed

8. Pressure is the amount of force distributed over an area
Force (Newtons)
Pressure
Area (Square meters – m2)

9. The SI unit of pressure is a Pascal (Pa)
Newtons per square meter (N/m2) is known as a Pascal
This unit is often changed to kilopascals (kPa)

10. Practice
A box with a weight of 2700 Newtons is resting on the ground. If the area of the box touching the ground is 1.5 square meters, then what pressure does the box exert on the ground?
Force
2700 N
Pressure
1800 N/m2
Area
1.5 m2
1800 N/m2
1800 Pa or 1.8 kPa

11. Pressure in Fluids Pressure in a non-moving fluid is determined by:
Type of fluid (Density is different for each)
Depth within the fluid
Pressure increases as depth increases

12. Pressure in Fluids (continued)
Pressure at any depth is constant and is exerted equally in all directions

13. Pressure in Fluids (continued)
The amount of a fluid in regards to volume or weight
does not affect pressure (Page 392 – Figure 3)

15. 1 Pascal is not much pressure but even our atmosphere exerts pressure on us

16. Atmospheric pressure = about 101,300 pascals

17. Empty bottle sealed at 14,000 feet
Same bottle at 9,000 feet
Same bottle at 1,000 feet

18. The amount of available oxygen becomes less and less as you move to higher elevations

19. Certain types of weather are accompanied by pressure changes

20. Fluids will move from a high pressure to a lower pressure