APPLYING PASCAL’S PRINCIPLE

Pressure act on a solid object:Pressure = Normal force

area P =

Pressure at any point in liquid acts in all directions. Also increases with depth and affected by gravitational force

A

F

ghP

At the end of the lesson, student is able to:a.state Pascal’s principle:

b.explain hydraulic system

What happen to the pressure that is exerted upon an enclosed fluid?

Stated that an external pressure applied to an

enclosed fluid is transmitted equally to every part of the

fluid, as well as to the enclosed wall

You’re driving along quite happily when, all of a sudden, a dog runs out into the road just in front of you. You have a split second to react to what's happened. When you stamp on the brakes, you confidently expect they'll bring you to stop moving in time. How does it happen?

Photo: The brake disc on a car is the small, metal wheel just inside the silver spokes of the outer, alloy wheel. When you put the brakes on, a brake pad clamps onto this metal wheel to slow you down.

When your foot presses the brake lever, brake fluid squeezes out of a narrow cylinder, through a tube, into a much wider cylinder. This system, known as hydraulics, greatly increases the pushing force.

• a system of fluid-filled pipes that can multiply force and transmit it easily from one place to another.

• Force applied at one point is transmitted to another point using an incompressible fluid

Hydraulic system act as a force multiplier How does it work? The input force is multiplied by a certain

factor to gain a larger output force. In two connected pistons, a force at the

smaller diameter piston creates a greater force at the larger diameter piston

As the pressure is transmitted equally,P1 = P2

Output Force = Output Piston areaInput Force Input Piston area

Therefore,

1

212

A

AFF

2

2

1

1

A

F

A

F

1

2

1

2

A

A

F

F

What are the multiplication factors to gain a larger

output force?

1. The force, F1, applied to the small piston

2. The ratio of the surface areas of the pistons,

1

2

A

A

F220 N

Oil

Piston X

Area2 cm22

Load

Piston YArea 50 cm2

A basic hydraulic system has small and large pistons with cross-sectional

areas of 2 cm2 and 50 cm2 respectively. When a force of 20 N is applied to

the small piston, it pushes down the piston by 20 cm. Calculate

(a)The pressure transmitted in the hydraulic fluid,

(b)The force acting on the large piston

(c)The magnification of the force

a) F1 = 20 N

A1 = 2 cm2 = 2x10-4 m2

Pressure transmitted, P1 =

b) c) Magnification of force

Force on the large Piston, F2

1

1

A

F

224100000

102

20

Nm

m

N

2322

212

10550

100000

mcmA

NmPP

N

mNm

AP

500

105100000 232

22

timesN

NF

F

2520

5001

2

At the end of the lesson, student is able to:a.state Pascal’s principle:

in an enclosed fluid, an externally applied pressure is transmitted equally to every part of the liquid.

b.explain hydraulic system

1. What do you understand about Pascal’s principle?

2. How does the Hydraulic system operate as a force multiplier?

PASCAL’S PRINCIPLEPASCAL’S PRINCIPLE

Hydraulic systemHydraulic systemPressurePressure

Force multiplier

Enclosed fluid

Describe that

Is transmitted equally in every part of a liquid in an

Applied in

And act as

Read “the applications of Pascal’s principle in everyday life”

Page 187: Practice 3.4 (solve problem involving Pascal’s principle)