1. What is a Fluid?
A substance that has the capacity to flow and assume the form of the container.

2. Examples?
All gases and liquids!

3. Fluids and the Particle Model
Water- particles held close together
- poured in glass, particles
slide over each other
- take form of glass
Air- particles further apart
- move in every direction to fill
space of the container

4. Fluid or not? Smoke → Fluid (and colloid) 2. Toothpaste→ Fluid
Hair Gel →
Sand in Hourglass →
Not a Fluid (doesn’t flow, forms pile)

5. Types of Fluids Compressible Fluids - fluid whose volume change
Ex. air
- gases are compressible fluids

6. Incompressible Fluids
- a fluid whose volume cannot be
varied. Ex. blood
- Liquids are incompressible fluids

7. What is Pressure?
Pressure is the result of a force applied in a perpendicular fashion to a surface.

8. Force:
-Force is an action that modifies the movement of an object or the shape of an object to change.
ex. Key when texting,
Playing with play dough
- produced by action, or attraction between objects.
ex. Sun and moon

9. Pressure & Particles
Pressure is the force exerted by particles when they collide with a constricting surface

10. Effect of Force on Pressure
If the force is varied, and the area is kept constant
1. If the force increases, then
pressure increases.
2. If the force decreases, then
pressure decreases.

11. Blocks on table
As more blocks are added the force increases, but the area stays the same.

12. Effect of Surface Area
If the Surface Area is varied, and the Force is kept constant
1. If the surface area increases,
pressure decreases.
2. If the surface area decreases,
pressure increases.

13. Which footwear would you use in deep snow?
Black snow boots
Snowshoes

14. Boots:
less surface area, more pressure
→SINKING IN SNOW!
Snowshoes:
More surface area, less pressure
→YOU DON’T SINK

15. Mathematical Equation
P = F A
P: Pressure in N/m2
F: Force in N (newton)
A: Surface Area in m2

16. Pressure measured in units called:
Pascals(Pa), 1 Pa=1 N/m2 (very small)
1 kPa=1000 Pa= 1000 N/m2
Atmospheric Pressure=Air Pressure
(at sea level)
101.3 kPa=760 mm hg= 1 atm

17. Ex. 1 What is the pressure exert?
F= 1000 N
10 m
10 M
A= l x w
A= 10 m x 10 m
A= 100 m2
P = F/A= 1000N/ 100 m2
P = 10 N/m2
P= 10 Pa

18. Ex. 2 What is the force applied below?
P = 20 Pa
A= l x W= 15m x 10m
A= 150 m2
P = F A
20 Pa = F
150 m2
F = N
10 m
15 m

19. Ex. 3 :
What is the pressure in kPa exerted when 100 N of force is applied to a cylinder with a radius of 10 cm?
r=10 cm = 0.1 m
A= ∏r2
A= (3.14)(0.1 m)2
A= m2

20. P = F A
P= 100 N m2
P = 3185 Pa
P = 3185 Pa ÷ 1000 = 3.19 kPa

21. Incompressible Fluid
The FORCE exerted comes from the mass of the fluid that is situated ABOVE the object
If more fluid above, greater force
exerted by fluid, more pressure.

23. Density and Pressure
The more dense the fluid , the greater the pressure, and the less dense, the lower the pressure.
ex. Sea water d=1.03 g/cm3
Distilled Water d= 1.00 g/cm3

24. Compressible Fluid The number of collisions involving
fluid particles and other fluid
particles or objects

25. Factors that Affect Pressure
# of particles, more particles, more
pressure
Temperature- temp.,faster particles
more collisions

27. Pressure and Volume (Boyle’s Law)

28. Pressure
If pressure , then volume
Ex. Weather balloon rises,
volume , pressure as altitude
(balloon pops!)

30. The Ear External Pressure , the eardrum swells
Discomfort disappears when pressure becomes normal

31. Low pressure
High Pressure

32. General technical principles
A fluid naturally moves from a zone of high pressure toward a zone of low pressure

34. Second Principle
Pressure applied to the surface of a fluid inside a closed container gets uniformly distributed to every part of the fluid (Pascal’s principle)
Ex. Car brakes

36. Third Principle
A transfer of pressure in a fluid can increase the force involved.
Ex. Hydraulic Car Lift

38. Natural Mechanisms Heart works like a ________:
- _______________causes blood
to circulate
- ___________Pressure
(maximum pressure, heart beating)
(minimum pressure, heart resting)

39. Sphygmomanometer(mm Hg) (normal 120/75 Hg, 16/10 kPa)

41. 2. Inhalation and Exhalation
-Differences in pressure between the chest cavity and outside

42. 3.Bike pump
As the plunger goes down air is compressed into an increasingly smaller volume. As volume decreases, the pressure increases.
When the pressure is higher in the pump than the tire, then the air moves from the pump to the tire