1. VII. Forces in Fluids (Ch. 8.5)
Ch. 3 & 4 Motion & Forces
VII. Forces in Fluids (Ch. 8.5)
Archimedes’ Principle
Pascal’s Principle
Bernoulli’s Principle

2. A. Archimedes’ Principle
Fluid
matter that flows
liquids and gases
Buoyancy
the ability of a fluid to exert an upward force on an object immersed in it

3. A. Archimedes’ Principle
Bouyant Force
upward force exerted by a fluid on an immersed object
bouyant force > weight
balloon rises
bouyant force < weight
balloon sinks
bouyant force = weight
balloon floats

4. A. Archimedes’ Principle
the bouyant force on an object in a fluid is equal to the weight of fluid displaced by the object
Very little water needs to be displaced in order to cancel weight  ball floats on surface.
More water needs to be displaced in order to cancel weight  ball floats lower in the water.
Not enough water is displaced in order to cancel weight  ball sinks.
View Buoyancy JAVA Applet.
View animations produced by students at Poly Prep Country Day School in Brooklyn, New York.

5. View hydraulics explanation.
B. Pascal’s Principle
Pascal’s Principle
pressure applied to a fluid is transmitted unchanged throughout the fluid
View hydraulics explanation.

6. B. Pascal’s Principle Platform: 1000 N = F2 F = 1000 N 250 m2 10 m2
A car weighing 1000 N sits on a 250 m2 platform. What force is needed on the 10 m2 plunger to keep the car from sinking?
GIVEN:
Platform:
F = 1000 N
A = 250 m2
Plunger:
F = ?
A = 10 m2
WORK:
1000 N = F2
250 m m2
(1000 N)(10 m2)=(250 m2)F2
F2 = 40 N

7. C. Bernoulli’s Principle
as the velocity of a fluid increases, the pressure exerted by the fluid decreases
EX:airplane lift, curve balls

8. C. Bernoulli’s Principle
Airplane lift
Curve Ball
View airplane wings explanation.

9. C. Bernoulli’s Principle
Funnel Demos
View funnel explanation.
View inverted funnel explanation.

10. C. Bernoulli’s Principle
Venturi Effect
fluids flow faster through narrow spaces causing reduced pressure
EX: garden sprayer, atomizer, carburetor

11. C. Bernoulli’s Principle
Venturi Effect - Atomizers
View atomizer explanation.