Contributed by:

Pressure, Formula, Pressure and depth, Pascal's law, Hydraulic devices

1.
Topic 3.5 – Pressure in

Fluids – PASCAL’S LAW

Unit 2 – Mix and Flow of Matter

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!!!!

• 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

• 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)

• 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

• 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?

• 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?

• 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.

• 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

• 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

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.

• 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.

• 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

• 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?

5m2 50m2

• Study the diagram below. If the input

force is 100N, what is the output

force?

5m2 50m2

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.

• 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.