Unit 8 C: Fluids (Pg. 178 - 257)
Chapter 9: Density and Buoyancy (pg. 226 - 257)
Name: __________________________
Date: ___________________
9. 1: Putting the Squeeze of Fluids (Pg. 228 - 229):
Read Pages 228 - 229. Answer the following questions:
1 & 2: See PB pg. 187 (same questions)
3.
a) What is a hydraulic system?
A hydraulic system is a system that uses liquids under pressure to perform work.
b) What is a pneumatic system?
A pneumatic system is a system that uses gases under pressure to perform work.
4. What are the components of both hydraulic and pneumatic fluid systems?
Components of both hydraulic and pneumatic systems are pumps, conductors, valves, and pressure
gauges.
9.5: Relationships: Pressure, Volume, and Temperature (Pg. 238 – 239):
Read Pages 238 - 239. Answer the following questions.
1.
What happens to the volume of a gas in a cylinder when you try to compress it? Use a diagram in your
explanation.
When gas in a cylinder is compressed, its volume decreases as its particles are forced closer together, as
shown right.
2.
How is the property of compressibility of gases used in everyday life? Give an example.
Many products, such as air fresheners and scuba tanks, contain gases. Because gases can be compressed,
it is possible to fit a large amount of gas into a relatively small container.
3.
Explain why the barrel of a bicycle pump heats up when you use it to pump a tire.
When a bicycle pump is used to pump up a tire, the air in the barrel gets compressed as it is pumped; the
compression causes the air’s temperature to increase. The barrel of the bicycle pump also gets hot
because of the friction between the piston and the barrel.
4.
Why is heating an aerosol can be so dangerous?
Aerosol cans contain gas under high pressure. If a can is heated, the pressure inside the can will increase.
If the pressure gets too high, the can could explode.
9.4: Effects of External Pressure of Fluids (Pg. 234 - 236):
Read Pages 234 - 236. Answer the following questions:
1.
What is meant by “pressure” in a scientific sense? What units are used to measure pressure?
Scientifically, pressure is a measure of the force applied to a unit of surface area. It is measured in Pascal,
or Newton per square meter.
[P = F 
A
Pa = N/m2]
2.
In your own words, describe atmospheric pressure and water pressure.
Atmospheric pressure is the weight of Earth’s atmosphere pressing on a surface. Water pressure is the
force of water pressing on a surface.
3.
Describe Pascal’s Law in your won words. You may use a diagram to help.
Pascal’s Law states that a force applied to a contained fluid is transferred throughout the fluid equally in
all directions.
Problem Solving:
Note: Pascal’s Law works just like these other formulas that you are familiar with.
P=F
A
A=F
P
F
F=PxA
P
1.
If a force of 100 N is applied to a piston in a hydraulic cylinder of 4 m2 area, what is the pressure?
P = F = 100 N = 25 N/m2 = 25 Pa
A
4 m2
2.
If we have 50 N of force applied to an area 0.5 m2, what would be the pressure?
P = F = 50 N = 100 N/m2 = 100 Pa
A
0.5 m2
3.
If 80 N/m2 of pressure is applied to a 2 m2 area. What is the total force?
F = PA = 80 N/m2 x 2 m2 = 160 N
4.
A
If total force is 120 N and pressure is 30 N/m2, what is the area?
A = F = 120 N = 40 m2
P
30 N/ m2
9.7: The Value of Valves (Pg. 242 – 243):
Read Pages 242 – 243. Answer the following questions.
1.
What kind of system – hydraulic or pneumatic – is the human circulatory system?
The human circulatory system is a hydraulic system.
2.
What is the role of valves in the human circulatory system?
Valves in the circulatory system keep blood flowing in the right direction.
3.
In the human circulatory system, what is one result from a valve that does not work properly?
If the valves in the veins in the legs do not work properly, blood can pool in the veins and cause varicose
veins.
4.
What is the function of valves in the internal combustion system of a car engine?
The valves in an internal combustion engine serve three purposes: they regulate when air enters the
engine, they keep air and fuel gases from escaping the reaction chamber, and they regulate when waste
gases exit the engine.
9.8: The Power of Fluids (Pg. 244 – 245):
Read Pages 244 – 245. Answer the following questions.
1. What is a hydraulic ram?
A hydraulic ram is a hydraulic system consisting of a piston and cylinder. Hydraulic rams use
pressurized liquid to produce large amounts of force.
3. What is one advantage of using pneumatic power over hydraulic power?
One advantage to using pneumatic power instead of hydraulic power is that the fluids used in most
pneumatic systems are non-toxic, so if there is a leak, there is no environmental damage.
Chapter 9 - Review (pages 250 - 251)

What Do You Remember?
2. Give two examples each of hydraulic systems and pneumatic systems. K
Hydraulic: The human circulatory system and the hydraulic ram in a backhoe.
Pneumatic: The system that powers a pneumatic hammer and the system that opens and closes bus doors.
/U
3. What components make up a typical fluid system?
A typical fluid system consists of: pumps, valves, and a pressure gauge.
4. In your notebook, complete Table 1 using the terms “increases” or “decreases” to replace the blanks.
SEE PB pg. 197 Table 1
5.
(a) Define “pressure” in your own words.
Pressure is the force pressing against the surface of something. Pressure can be applied in any direction,
from the outside or from within.
(b) What units are used for measuring pressure? K/U
Pressure is measured in Pascal, which are equivalent to the force in Newton per square meter of surface
area.
6. In which direction does air pressure push on your body? K/U
Air pressure pushes against your body in all directions.
7. What does Pascal’s Law state?
Pascal’s Law states that a force applied to a contained fluid is transferred throughout the fluid equally in
all directions.
8. Describe one way in which modern machinery uses Pascal’s Law.
Pascal’s Law is used today in devices, such as hydraulic brakes. Brakes need to apply a controlled force
equally across a moving part; fluids transfer forces in such a way as to achieve this.
K/
9. Explain the importance of valves in the human circulatory system. K
Valves control the direction of blood flow in the human circulatory system. Valves open and close to keep
blood flowing in the correct direction throughout the body.
/U
10. How are hydraulic and pneumatic systems similar? How are they different?
Similar: They both use pressurized fluids to do work. Both systems contain the same basic components,
such as pumps and conductors.
Different: Hydraulic systems use pressurized liquids and pneumatic systems use gases.
11. How are atmospheric pressure and water pressure similar? How are they different? K/
Similar: They both act in all directions and are caused by the force of moving particles pressing against a
body.
Different: Water particles are heavier than air particles and are packed more tightly together. Therefore,
water pressure is greater than atmospheric pressure, if the depth of both fluids is the same.
U

What Do You Understand?
21. Describe how the air pressure inside a tennis ball changes when you hit it.
When a tennis ball is hit, the side that touches the racquet is forced inward. This compresses the ball
(decreases its volume). When the volume of a gas decreases, its pressure increases. Therefore, the
pressure inside the tennis ball probably increases when it is hit.
22. A scuba diver stays underwater for about 30 minutes. How is this possible when the air tank on her back is
so small? K/U A
A scuba diver’s air tank is filled with highly compressed air. The air particles are squeezed tightly
together, which allows a lot more air to fit inside the tank than if the air had not been compressed. The
gas is allowed to decompress before the diver breathes it.
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