1. Topic 3.5 – Pressure in Fluids – PASCAL’S LAW
Unit 2 – Mix and Flow of Matter

2. UNITS Alright grade 8’s… Name me as many units as you can think of…
Ready…
GO!!!!

3. Pressure Pressure is the amount of force applied to a given area.
Measured in pascals (Pa)
A pascal equals the force of 1 N (newton) over an area of 1 m2
The MORE force you can apply to an area, the GREATER the pressure

4. Formula The formula for calculating pressure is: P = F A
P = pressure (Pa)
F = force (N)
A = area (m2)

5. Example
You have a force of 10 N on an area of 2 m2. What would the pressure be?
Area = 2 m2
Force = 10 N
Pressure = ?
P = 10 N
2 m2
P = 5 Pa

6. Kilopascals A pascal is a VERY SMALL amount of pressure.
Most scientists will measure pressure in kilopascals (kPa)
1 kPa = 1000 Pa
A ballet dancer standing on the toes of ONE foot exerts 2500 kPa of pressure on the floor.
How many pascals is this?

7. Pressure and Depth
Water in a tin can is exerting pressure on all the walls of the tin can
If we were to punch TWO holes in this tin can, how would the water come out?

8. Tin can experiment
The water is coming out almost in the exact same way.
Why is this?
The weight of the water in the upper part of the tin can is pressed down on the water in the lower part.
The more water above the hole, the more pressure.

9. Pascal’s Law Meet Pascal --------
Handsome man eh?
Pascal developed a law to explain how pressure is equal in all directions in fluids

10. Pascal’s Law states that an enclosed fluid transmits pressure EQUALLY in all directions.
Let’s look at some examples to figure out what the heck this handsome man (haha) is trying to tell us 

11. Hydraulic Devices Hydraulic systems use a liquid as the enclosed fluid
Just like we saw in Bill Nye with the cars.

12. Car lifts

13. Advantages to Hydraulic Systems
In the lift we just saw, the output force is 16 TIMES greater than the input force.
A benefit of this type of system is it can multiply force.

14. Pneumatic Systems Pneumatic systems use air to do tasks.
Examples of this would be
Dentist drills, jack hammers, paint sprayers and air brakes on trucks
These cost less and are more safe than hydraulic systems

15. Example
Study the diagram below. If the input force is 100N, what is the output force?
50m2
5m2

16. Maintaining Pressure
For a hydraulic and pneumatic system to function properly, the entire system must be SEALED
The smallest hole or leak causes the system to fail.