Chapter 8 Force and Pressure

8 Force and
pressure

Theme 3: Energy and Sustainability of Life

• Pressure in fluids: Tekanan dalam cecair Keywords
• Pascal’s Principle: Prinsip Paskal/Tekanan
• Enclosed system: Sistem tertutup
• Hydraulic system: Sistem hidraulik
• Hydraulic jack system: Sistem bicu hidraulik
• Hydraulic brake system: Sistem brek hidraulik
• Disc brake: Brek cakera
• Drum brake: Brek dram
• Dental chair: Kerusi pergigian
• Venturi tube: Tiub pengudaraan
• Venturi effect: Kesan pengudaraan
• Bernoulli’s principle: Prinsip Bernoulli
• Lift: Angkat
• Aerofoil shape: Bentuk aerofoil
• Crane: Kren

8 Force and Pressure : Keywords

Science bulletin

Have you ever heard a loud hissing sound made by
a heavy vehicle such as a tour bus or oil tanker
when the vehicle stops? What is the system that

operates in the heavy vehicles and produces this
loud hissing sound?

8 Force and Pressure : Science Bulletin

Science bulletin

Video: Emergency braking of Volvo trucks
https://www.youtube.com/watch?v=ridS396W2BY

8 Force and Pressure : Volvo Trucks - Emergency braking at its best! By Volvo trucks https://www.youtube.com/watch?v=ridS396W2BY

Light motor vehicles such as
cars normally use hydraulic
brakes. Heavy motor vehicles
such as busses and lorries use
air brakes that produce a larger
frictional force to stop the

motion of the vehicle.
Nevertheless, both hydraulic
brakes and air brakes use a

system which applies
Pascal’s Principle.

8 Force and Pressure : Science Bulletin

8.1

Pressure in fluids

• Concept of Pressure in Fluids in an Enclosed System
• Application of Pascal’s Principle in Daily Life

• Relationship between Fluid Velocity and Pressure
• Application of Bernoulli’s Principle in Daily Life

8 Force and Pressure : 8.1 Pressure in Fluids

Concept of pressure in fluids in an enclosed system

● This device operates based
on the effect of pressure in

hydraulic

● An enclosed system is a
physical system where
matter cannot enter or leave
Photograph 8.1 Hydraulic jack

the system

8.1 Pressure in Fluids : Concept of pressure in fluid in an enclosed system

Concept of pressure in fluids in an enclosed system

• Based on Figure 8.1 (a) water from
the bottommost hole shoots out
the further from the upper holes
due to the pressure in the water

• If force is applied to the water
surface by compressing the
closed plastic bottle, water from
each hole will shoot further at
equal additional distance as
shown in Figure 8.1(b)

Figure 8.1 Uniform transmission of pressure in water in a closed plastic bottles

8.1 Pressure in Fluids : Concept of pressure in fluid in an enclosed system

Concept of pressure in fluids in
an enclosed system

Pascal’s principle states that the
transmission of pressure exerted

on a fluid (liquid or gas) in an
enclosed system is uniform
throughout the fluid and in all

directions

8.1 Pressure in Fluids : Concept of pressure in fluid in an enclosed system

Concept of pressure in fluids
in an enclosed system

8.1 Pressure in Fluids : Concept of pressure in fluid in an enclosed system

Pascal’s principle

Pascal’s Principle video: https://www.youtube.com/watch?v=RoSrtt-i9HU

Pascal’s Principle by Science Project https://www.youtube.com/watch?v=RoSrtt-i9HU



Answer

8.1 Pressure in Fluids : Activity 8.1

Operating Principle of
Hydraulic System

Pascal’s principle is
commonly applied
in daily life such as
in the operation of
hydraulic system

8.1 Pressure in Fluids : Operating principle of hydraulic system

Hydraulic system

Principle uses operation

The basic principle in The hydraulic Study and
a hydraulic system is system is used to understand the
the transmission of do heavy work such following example
which shows the
pressure in all as producing a operation of the
directions based on large output force hydraulic system
to lift heavy loads
Pascal’s principle

8.1 Pressure in Fluids : Hydraulic System

Operating principle of hydraulic system

1The hydraulic system is 2 The fluid commonly
made up of two used is water or oil.
cylindrical pistons of
different surface areas According to Pascal’s
principle, the presure
3Water or oil is used
4 exerted by the small
because they do not piston is the same as
have a fixed shape and the pressure produced
cannot be compressed at the large piston

8.1 Pressure in Fluids : Operating principle of hydraulic system

Operation of hydraulic system

8.1 Pressure in Fluids : Operation of hydraulic system

Operation of hydraulic system

8.1 Pressure in Fluids : Operation of hydraulic system

Application of pascal’s principle in daily life

• The hydraulic system is used to carry out heavy work using a small force.
• Three examples where Pascal’s principle is applied in daily life are as follows:

1 23

Hydraulic jack system Dental chair Hydraulic brake system

8.1 Pressure in Fluids : Application of Pascal’s Principle in Daily Life

Hydraulic Jack system

Photograph 8.2 Hydraulic jack

Hydraulic jack is usually
used to lift heavy loads
such as cars in
workshops.
● Try operating a hydraulic jack.
● Figure 8.5 shows the structure of a hydraulic jack
system.

8.1 Pressure in Fluids : Hydraulic Jack System

Hydraulic Jack system

In the hydraulic jack system, the
lever is moved downward and
upwards repeatedly to push the
loaded large piston upwards with
the release valve closed

When the release valve is opened,
the loaded large piston will drop
back to its original position

8.1 Pressure in Fluids : Hydraulic Jack System

Hydraulic jack system Video:
https://www.youtube.com/watch?v=iCwwOzb9-as

Hydraulic Physics (How Hydraulic Jacks Work) by VAM! Physics & Engineering https://www.youtube.com/watch?v=iCwwOzb9-as

8.1 Pressure in Fluids : Operation of hydraulic jack system

8.1 Pressure in Fluids : Operation of hydraulic jack system

8.1 Pressure in Fluids : Operation of hydraulic jack system

THE Hydraulic BRAKE system

The hydraulic brake system is
commonly used to slow down or
stop wheeled vehicles such as
moving cars.

The operation of a hydraulic
brake system is shown the next
figure.

8.1 Pressure in Fluids : The Hydraulic Brake System

The Hydraulic Brake System

Figure 8.9 Hydraulic brake system and its operation

8.1 Pressure in Fluids : The Hydraulic Brake System

The Hydraulic Brake System

8.1 Pressure in Fluids : The Hydraulic Brake System

Hydraulic brake system Video:
https://www.youtube.com/watch?v=CzEBVdZeyQs

Animated Hydraulic Car Braking System by asakatali https://www.youtube.com/watch?v=CzEBVdZeyQs

Dental chair

The operation of the dental chair is
related to the hydraulic system.

Photograph 8.3 Dental chair

8.1 Pressure in Fluids : Dental Chair

Hydraulic dentist chair Video:
https://www.youtube.com/w
atch?v=j8014X9fjK4

Hydraulic dentist chair by Maddielovesherdogs https://www.youtube.com/watch?v=j8014X9fjK4

Relationship between fluid velocity and pressure

8.1 Pressure in Fluids : Relationship between fluid velocity and pressure

Relationship between fluid velocity and
pressure

8.1 Pressure in Fluids : Relationship between fluid velocity and pressure

Relationship between fluid
velocity and pressure

• When the fluid flows
through the narrow part,
its velocity increases and
the pressure in that region
decreases.

• This is known as Bernoulli’s
principle.

8.1 Pressure in Fluids : Relationship between fluid velocity and pressure

Video: venturi effect and Bernoulli’s principle

https://www.youtube.com/watch?v=eUIUqc4aay0

Bernoulli's Principle (Venturi Effect) | Force and Pressure by myhometuition https://www.youtube.com/watch?v=eUIUqc4aay0

8.1 Pressure in Fluids : Activity 8.2

8.1 Pressure in Fluids : Activity 8.2

Answer

8.1 Pressure in Fluids : Activity 8.2 - Answer

Application of
bernoulli’s
principle in
daily life

Application of bernoulli’s principle

Bernoulli’s principle states that a fluid moving at a higher velocity
produces a lower pressure in that region

Aerofoil-shaped 1 2 Bunsen burner

wings of an
aeroplane

Safety lines near 5 3 Helicopter
4 Drone
railways track at a
railway station

8.1 Pressure in Fluids : Application of Bernoulli’s Principle

bernoulli’s principle in daily life

8.1 Pressure in Fluids : Application of Bernoulli’s Principle

bernoulli’s principle in daily life

8.1 Pressure in Fluids : Application of Bernoulli’s Principle

bernoulli’s principle in daily life

8.1 Pressure in Fluids : Application of Bernoulli’s Principle

8.1 Pressure in Fluids : Application of Bernoulli’s Principle – Activity 8.3

8.1 Pressure in Fluids : Application of Bernoulli’s Principle – Activity 8.4

Answer

8.1 Pressure in Fluids : Formative Practice 8.1

8.1 Pressure in Fluids : Summative Practice 8

8.1 Pressure in Fluids : Enrichment Practice

Answer

8.1 Pressure in Fluids : Summative Practice 8 - Answer

THANKS!

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‘teCHer Herlina
SMKCB

Science Form 5 Textbook (DLP), KPM

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