1. Gas Laws
Lesson 2

2. Properties of Fluids A fluid is a gas or a liquid
despite their weight ships are able to float.
greater force pushing up on the ship opposes the weight—or force—of the ship pushing down.

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

4. Archimedes’ Principle
the buoyant 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.
Not enough water is displaced in order to cancel weight  ball sinks.
More water needs to be displaced in order to cancel weight  ball floats lower in the water.
View Buoyancy JAVA Applet.
View animations produced by students at Poly Prep Country Day School in Brooklyn, New York.

5. Density
object will float if its density is less than the fluid it is in.
Suppose you form a steel block into the shape of a hull filled with air. Now the same mass takes up a larger volume. The overall density of the steel boat and air is less than the density of water. The boat will now float.

6. Pascal’s Principle Pressure is force exerted per unit area
Blaise Pascal ( ),
a French scientist, discovered a useful property of fluids.
Pascal’s principle
pressure applied to a fluid is transmitted throughout the fluid.
Ex: toothpaste, hydraulic lifts

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

8. Applying the Principle
pipe filled with fluid connects small and large cylinders.
pressure applied to the small cylinder is transferred through the fluid to the large cylinder

9. Applying the Principle
pressure remains constant throughout the fluid
more force is available to lift a heavy load by increasing the surface area.

10. Pascal’s Principle Platform: F = 1000 N A = 250 m2 Plunger: F = ?
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

11. Pascal’s Principle Platform: F = 1000 N A = 5 m2 Plunger: F = ?
A disgruntled cow that weighs 1000 N sits on a 5 m² piston. What force would need to be applied to a 2 m² piston?
GIVEN:
Platform:
F = 1000 N
A = 5 m2
Plunger:
F = ?
A = 2 m2
WORK:
1000 N = F2
5 m m2
(1000 N)(2 m2)=(5 m2)F2
F2 = 400 N

12. Bernoulli’s Principle
as the velocity of a fluid increases, the pressure exerted by the fluid decreases
EX:airplane lift, curve balls
Bernoulli – why planes fly

13. Bernoulli’s Principle
demonstrate Bernoulli’s principle
blow across the top surface of a sheet of paper.
The paper will rise.
velocity of the air over the top is greater than that of the quiet air below it.
Net force below raises the paper

14. Bernoulli’s Principle
Airplane lift
The downward force decrease and
the lifting force increases. Bernoulli’s
principle states that as the velocity
of a fluid increases the pressure exerted
by the fluid decreases.
View airplane wings explanation.

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

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

17. Bernoulli’s Principle
This allows the water in the hose to flow at a high rate of speed, creating a low pressure area above the strawlike tube.
The concentrated chemical solution is sucked up through the straw and into the stream of water.
The concentrated solution is mixed with water, reducing the concentration to the appropriate level and creating a spray that is easy to apply.

18. Fluid Flow
Another property exhibited by fluid is its tendency to flow. The resistance to flow by a fluid is called viscosity.
When a container of liquid is tilted to allow flow to begin, the flowing particles will transfer energy to the particles that are stationary.
Temperature and viscosity are inversely related; that is higher temperature means lower viscosity

19. Fluid Flow
In effect, the flowing particles are pulling the other particles, causing them to flow, too.
If the flowing particles do not effectively pull the other particles into motion, then the liquid has a high viscosity, or a high resistance to flow.
If the flowing particles pull the other particles into motion easily, then the liquid has low viscosity, or a low resistance to flow.

20. Temperature and viscosity are inversely related; that is higher temperature means lower viscosity