1. Fluid Pressure
Chapter 13 Section 1
Page 390

2. Objectives You should be able to explain what pressure depends on.
You should be able to explain how fluids exert pressure.
You should be able to describe how fluid pressure changes with elevation and depth.

3. Fluid Pressure
Chapter 13 Section 1 Pg

4. Have you wondered…?

5. Pressure The result of a _____ distributed over an ____ So…
The ______ the area over which the force is distributed, the less pressure is _______.
Ex: a pencil point has a much smaller area than the eraser, so it exerts much _______ pressure than the eraser.

6. Surface Area of my bare feet = 400.0 cm2
Surface Area of my boots = cm2
Surface Area of my snowshoes = cm2

7. Calculating Pressure

8. Units _____- measured in newtons (N)
Area- measured in ______ meters (m2)
_______- SI unit is newton per square meter (N/m2)
Also called ______ (Pa)
1 N/m2 = 1 Pa
Named for French scientist ______ Pascal
Pressure is often in ___
1 kPa = 1,000 Pa

9. Practice Problem
Calculate the pressure produced by a force of 800 N acting on an area of 2.0 m2.
P = F/A
P = (800 N)/(2.0 m2)
P = 400 N/m2 = 400 Pa = 0.4 kPa

11. Fluids ______ also exert a pressure
Fluid is a material that can easily flow
Fluids take ____ of container
Liquids and ______ are fluids

12. Cause of Fluid Pressure
Fluid particles ______ with a surface, exerting a force on the surface
All of the forces exerted combine to make up the ________ exerted by the fluid
The ______ of particles in a fluid is large, so a fluid can be considered as a whole.

13. Fluid Pressure
Determined by the ____ of fluid and its depth

14. Fluid Pressure Water ________ increases as depth increases.
The pressure at any given depth is constant, and it is ______ equally in all directions.

15. Why do ears “pop”?

16. Air Pressure Earth’s _________ is made up of a mixture gases
Atmospheric pressure = 101 kPa at ________
___ pressure decreases as the altitude increases

18. How does a straw work?

19. Review

20. 1. Order from lowest to highest pressure.
A<B<C
C<B<A
all are equal A

21. 2. Look at the markers. Order from lowest to highest pressure.X
A. Y<Z<X B. Y<X<Z C. Z<X<Y
D. X<Z<Y E. two are equal Y E Z

22. 3. What will happen to the pressure if more water is added?
increase
decrease
stay the same A

23. increase decrease stay the same
4. What will happen to the pressure if more water is added while the same amount is removed?
increase
decrease
stay the same C

24. increase decrease stay the same
5. What will happen to the pressure if the fluid were changed to honey?
increase
decrease
stay the same A

25. increase decrease stay the same
6. If the 250 kg mass was put on the water column, what will happen to the pressure? A
increase
decrease
stay the same

26. increase by 101.3 kPa decrease by 101.3 kPa stay the same
7. If the only change was to remove the air pressure , what will happen to the pressure?
increase by kPa
decrease by kPa
stay the same
Something else B

27. 8. If the only change was to go to a place where the gravity was doubled, what will happen to the pressure?
Both pressures would double
Only the air pressure would double
The air pressure would double, and the water pressure would increase some
Something else A

28. 9. How do the pressures at the two locations compare?X Y
9. How do the pressures at the two locations compare? C
X>Y
Y>X
They are the same

29. Review
What is the relationship between the depth of water and the pressure it exerts?
How is pressure distributed at a given level in a fluid?
How does the pressure exerted by the atmosphere change as altitude increases?
Why don’t you feel the pressure exerted by the atmosphere?

30. Review
A 500 N student stands on one foot. A 750 N student stands on two feet. If both students wear the same size shoe, which exerts the greater pressure?
A circus performer on a pair of stilts exerts a pressure of 32 kPa on the ground. If the performer stands on one stilt, what pressure does the stilt exert on the ground?

32. Forces and Pressure in Fluids
Chapter 13 Section 2 Pg

33. Transmitting Pressure in a Fluid
Recall:
A _____ exerts pressure equally in all directions at a given _____.
The amount of pressure exerted by a fluid depends on the ____ of fluid and its depth.

34. Pascal’s Principle
Note that the pressure increases _______ throughout the water, not just at the _____ where you squeeze- discovered by Pascal in 1600s.
According to _______ principle, a change in pressure at any point in a fluid is transmitted equally and ___________ in all directions throughout the fluid.

35. Hydraulic Systems
A hydraulic system is a device that uses __________ fluid acting on pistons of different sizes to change a force.
An ________ output force is produced because a _______ fluid pressure is exerted on the ______ area of the output piston.

36. Hydraulic Systems
In the picture, an _____ force is applied to the small piston, which pushes against the fluid sealed in the _________________.
Due to Pascal’s principle, we know that the pressure produced by the small piston is ________ through the fluid to the large piston.
The pressure on both pistons is the ____. However, the pressure pushing against the large piston acts on a much larger ____, which is the key to how the system works.
The large _____ force is used to lift and dump the load.
The amount the input force is increased depends on the _____ of the pistons.
If the large piston has 8 times the area of the _____ piston, then the output force is 8 times greater than the input force

37. Bernoulli’s Principle
Get out a piece of paper
Daniel Bernoulli- _____ scientist
________: as the speed of a fluid increases, the pressure within the fluid _________
As the air blows _____ the top of the paper, the pressure exerted by the air decreases. Because the air below the paper is nearly __________, it exerts a greater pressure. The difference in pressure forces the paper ________.

38. Bernoulli’s Principle
Wings and Lift
_________ principle help explain the flying ability of birds and airplanes.
Air traveling over the ___ of an airplane wing moves faster than the air passing underneath, creating a ___________ area above the wing.
The pressure difference between the top and the bottom of the wing creates an upward force known as a _____
Wings of birds produce a similar lift to airplanes, but birds can flap their wings to produce _______ movement and some lift
Wings can also be used to create a downward force: race cars often have a ______ (upside-down wing) to give better traction

39. Bernoulli’s Principle
Spray Bottles
Think of a hose-end sprayer. (Often used to apply fertilizers)
A _________ solution of a chemical is placed in the solution chamber and the sprayer is then attached to a hose.
As water streams through the sprayer, it passes over the ___of a small tube that reaches down into the solution chamber. The fast-moving water creates a _______ area at the top of the tube which forces the solution up the tube where it then _____ with the water and is sprayed out of the end of the sprayer

40. Buoyancy
Chapter 13 Section 3
Page

41. Buoyant Force
_______ is the ability of a fluid to exert an upward force on an object placed in it
Buoyancy results in the apparent loss of ______ of an object in a fluid.
When an object is submerged in water, the water exerts an ______ force on the object, making it easier to lift.
The upward force acts in the _______ direction of gravity and is referred to as buoyant force

42. Buoyant Force How it is produced…
Since water pressure ________ with depth, the forces pushing up on the bottom of the object are greater than the _____ from pressure pushing _____ on the top of the object (any non-vertical forces cancel one another out), resulting in a net upward force- the buoyant force

43. Archimedes’ Principle
Archimedes- an ancient _____ mathematician
Archimedes’ Principle- the buoyant force on an object is equal to the weight of the fluid _________ by the object
When an object is submerged, it _____ aside, or displaces, a volume of fluid _____ to its own volume.
When an object _____ on the surface, it does not displace its entire volume. However, it does displace a volume equal to the ______ of the part of the object that is submerged

44. Density and Buoyancy
Recall: ______ is the ratio of an object’s mass to its volume
Density is often expressed in _____ of grams per cubic centimeter (g/cm3)
Water has a density of 1 g/cm3
Steel has a density of 7.8 g/cm3
If an object is ____ dense than the fluid it is in, it will float. If the object is ____ dense than the fluid it is in, it will sink.

45. Density and Buoyancy
The force of ______, equal to the object’s weight, acts ________ on the object.
The buoyant force, equal to the weight of the volume of ______ fluid, acts upward on the object.
When the buoyant force is _____ to the weight, an object floats or is suspended. When the buoyant force is ____ than the weight, the object sinks. (see pg. 401)

46. Density and Buoyancy Suspended Sinking
When an object has the ____ density as the fluid it is submerged in.
Buoyant force exactly ____ the object’s weight
Neutral buoyancy
Sinking
When an object’s weight is _____ than the buoyant force acting on it
________ buoyancy

47. Density and Buoyancy Floating
When the buoyant force is greater than the object’s weight
_______ buoyancy
Objects float more easily in _____ fluids
Heavy ships can float because of the _____ of the hull. It displaces a large volume of water, creating a _____ buoyant force
The ______ the fluid is, the greater is the weight displaced, which results in a greater buoyant force

48. Density and Buoyancy

49. Density and Buoyancy
See page 402 in your book for how a submarine works.

50. Works Cited
Frank, Wysession, & Yancopoulos. “Chapter 13 Forces in Fluids.” Physical Concepts in Action. Upper Saddle River: Pearson, Print.