1. Other Effects of Fluid Forces
Lesson 3
Other Effects of Fluid Forces
Chapter Menu

2. Lesson 3 Reading Guide - KC
Other Forces in Fluids
How are forces transferred through a fluid?
How does Bernoulli’s principle describe the relationship between pressure and speed?
What affects drag forces?
Lesson 3 Reading Guide - KC

3. Lesson 3 Reading Guide - Vocab
Other Forces in Fluids
Pascal’s principle
Bernoulli’s principle
drag force
Lesson 3 Reading Guide - Vocab

4. Fluid Forces—Benefits and Challenges
You produce a force when you squeeze a plastic ketchup bottle.
You make use of a buoyant force when you float on a raft.
Fluid forces from floods, tornadoes, and hurricanes can cause damage.
Lesson 3-1

5. Pascal’s Principle
Pascal’s principle states that when pressure is applied to a fluid in a closed container, the pressure increases by the same amount everywhere in the container.
Lesson 3-2

7. Pascal’s Principle (cont.)
How does pressure change when force is applied to a fluid in a closed container?
Lesson 3-2

8. Pascal’s Principle (cont.)
A piston uses a small force in one area to apply a larger force in another area.
According to Pascal’s principle, pushing on the piston increases the pressure equally throughout the fluid in the piston.
Lesson 3-2

9. Car mechanics rely on Pascal’s principle when they raise a car using a hydraulic lift.
Pushing down with a small force in the narrow tube generates a force under the car that is large enough to lift the car.
Lesson 3-2

10. The piston on the left will have to be pushed down further than the distance the car will be raised.
Since work is force times distance, the work done by the two pistons is equal.
Lesson 3-2

11. Any input force applied to the input piston results in an output force that is multiplied by the same ratio between the input and output distance.

15. Bernoulli’s Principle
Lesson 3-3

16. Bernoulli’s principle states that the pressure of a fluid decreases when the speed of that fluid increases.

17. Chimney

18. Bernoulli’s Principle (cont.)
What is the relationship between speed and pressure in a fluid?
Lesson 3-3

19. Bernoulli’s Principle (cont.)
Lesson 3-3

20. Bernoulli’s Principle (cont.)
How does Bernoulli’s principle explain how wind can take the roof off a house?
Lesson 3-3

21. Because air moves from areas of high to low pressure, the higher pressure on the left side of the soccer ball causes the ball to curve right.
Lesson 3-3

22. Drag Forces
Drag force is a force that opposes the motion of an object through a fluid.
drag force
from Old Norse draga, means “to draw”; and Latin fortis, means “force”
Lesson 3-4

24. Drag Forces (cont.)
As the speed of an object in a fluid increases, the drag force on that object also increases.
If two objects move in the same direction, the object with the greater surface area toward the direction of the motion has a greater drag force on it.
Drag forces increase when the density of a fluid increases.
Lesson 3-4

25. Drag Forces (cont.) What affects the drag force on an object?
Lesson 3-4

26. People rely on Pascal’s principle when they use hydraulic lifts.
The imbalance of pressures in fluids can cause a roof to lift off a house in a severe windstorm.
Lesson 3 - VS

27. A soccer player who kicks a curved ball makes use of Bernoulli’s principle.
Lesson 3 - VS

28. Which states that pressure in a closed container is applied equally?
A. Archimedes’ principle
B. Bernoulli’s principle
C. drag force principle
D. Pascal’s principle
Lesson 3 – LR1

29. A. More work is done on the larger side.
What is the relationship between the amount of work on the two pistons of a closed fluid system?
A. More work is done on the larger side.
B. More work is done on the smaller side.
C. No work is done on either side.
D. The amount of work is the same on both sides.
Lesson 3 – LR2

30. A. Archimedes’ principle B. Bernoulli’s principle
Which states that the pressure of a fluid decreases when the speed of that fluid increases?
A. Archimedes’ principle
B. Bernoulli’s principle
C. drag force principle
D. Pascal’s principle
Lesson 3 – LR3

31. 6. Running with an open parachute decreases the drag force on you.
Do you agree or disagree?
5. If you squeeze an unopened plastic ketchup bottle, the pressure on the ketchup changes everywhere in the bottle.
6. Running with an open parachute decreases the drag force on you.
Lesson 3 - Now