Unit 14 Simple machines

Lesson 1 Types of simple machines and Duration of lesson: 6 periods

their functions
Learning objectives
• Identify the different types of simple machines.
• Explain the functions of simple machines, which include multiplying force, multiplying speed and changing the
direction of a force.
• Recognise precautionary measures in using simple machines.

Engage (1st E) Use of an interesting picture or a demonstration (5 min)

Option 1
Purpose: To engage pupils and evaluate their prior knowledge about simple machines
Resource: Textbook

1. Have pupils turn to Textbook p. 19 and look at the picture. Give pupils some time to read the sentence at the
bottom of the page.
2. Ask pupils the questions that follow. Discuss the answers.
3. Go through the 'Let's find out' questions.

Option 2
Purpose: To engage pupils and evaluate their prior knowledge about simple machines
Resources: Textbook, a pen, a piece of paper, a correction tape dispenser

1. Use a pen to write on a piece of paper.

2. Show pupils a correction tape dispenser and use it to go over what you have written on the paper.
3. Show pupils the gears in the correction tape dispenser and tell pupils that it has two interlocking gears. Ask:
• What helps the gears to interlock and turn together? (the teeth on the wheels of the gears)
4. Have pupils turn to Textbook p. 19.
5. Go through the 'Let's find out' questions.

Explore (2nd E) Guided inquiry (10 min)

Purposes: To introduce the different types of simple machines and their functions
Resource: Textbook

1. Ask pupils the key inquiry questions for Section 14.1 on Textbook p. 20, Section 14.2 on Textbook p. 21,
Section 14.3 on Textbook p. 25, Section 14.4 on Textbook p. 28, Section 14.5 on Textbook p. 29, Section 14.6
on Textbook p. 30 and Section 14.7 on Textbook p. 31. Discuss possible answers.

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Explain (3rd E) Teacher-directed discussion (120 min)

Purposes: To explain the different types of simple machines and their functions
Resource: Textbook

1. Recall that our skeletal and muscular systems must work together for us to move and do work.
2. Have pupils turn to Textbook p. 20. Use the picture of the arm with the weight to explain that the force we
apply to do work is called the effort and the object that the effort moves or overcomes is called the load.
Point out that when we cannot lift a load that is too heavy, we need machines to help us.
3. Have pupils look at the pictures of the five types of simple machines on Textbook p. 20. Identify them and
explain the three main functions of simple machines.
4. Have pupils carry out the 'Explore' activity on Textbook p. 20. Discuss possible answers. (The muscles in our
arm are similar to the parts of a lever. The elbow joint is the fulcrum, the force applied by the muscles is the
effort and the object we hold in our hand is the load. Accept other possible answers.)
5. Have pupils turn to Textbook p. 21. Use the picture to explain to pupils the parts of a lever. Also explain the
two ways to reduce the effort needed to lift or move a load and the three types of levers.
6. Have pupils look at the That's Cool' feature on Textbook p. 21. Elaborate that trebuchets are siege machines
that can fling up to 140 kg of heavy objects into enemy grounds. During wars in the past, diseased corpses
were flung into enemy cities using trebuchets to infect the enemy population as a form of biological warfare.
7. Have pupils turn to Textbook p. 22 and look at the diagrams of a first-class and second-class lever. Explain to
pupils how first-class and second-class levers function.
8. Have pupils think about the 'Explore' question on Textbook p. 22. Discuss possible answers. (When we use
the spoon to open the lid of a tin, the lid that we lift is the load, the force applied by our hand is the effort and
the point at which the spoon is resting is the fulcrum.)
9. Have pupils turn to Textbook p. 23. Use the picture to show pupils some examples of first-class and
second-class levers.
10. Have pupils turn to Textbook p. 24. Use the diagram to explain to pupils how third-class levers function. Use
the pictures to show pupils some examples of third-class levers.
11. Have pupils think about the 'Explore' question on Textbook p. 24. Discuss possible answers. (Unlike other
types of levers, the effort is applied between the load and fulcrum in a third-class lever. Its function is to
multiply the speed of the force applied or effort. This effort may be greater than the load.)
12. Have pupils turn to Textbook p. 25. Use the picture to explain the parts of a pulley. Point out that there are
three types of pulleys.
13. Have pupils look at the diagram of a fixed pulley on Textbook p. 25 and use it to explain how a fixed
pulley functions.
14. Have pupils turn to Textbook p. 26 and use the diagram to explain how a movable pulley functions.
15. Have pupils turn to Textbook p. 27 and use the diagram to explain how pulley systems function. Point out to
pupils that pulley systems are found on ships and such a pulley system is called a block and tackle.
16. Have pupils look at the That's Cool' feature on Textbook p. 27. Elaborate that Leonardo da Vinci also came
up with the ideas for helicopters, tanks and calculators before these machines were actually invented.
17. Have pupils think about the 'Explore' question on Textbook p. 27. Discuss possible answers. (One type of
pulley that is commonly found in schools is on the flag pole that raises the flag. It is usually a fixed pulley.
Accept other possible answers.)
18. Have pupils turn to Textbook p. 28. Explain that a doorknob is an example of a wheel and axle. Also explain
the function of a wheel and axle and use the other pictures to show more examples of a wheel and axle.
19. Have pupils look at the That's Cool' feature on Textbook p. 28. Elaborate that the original Ferris wheel was
designed and constructed by George Washington Gale Ferris Junior in 1893 for an exposition in Chicago,
United States. The term 'Ferris wheel' later became known for all such structures.
20. Have pupils carry out the 'Explore1 activity on Textbook p. 28. Discuss possible answers. (A screwdriver is
a wheel and axle. The handle of the screwdriver is the wheel and the metal shaft or rod is the axle. Accept
other possible answers.)
21. Have pupils turn to Textbook p. 29 and use the pictures to explain how an inclined plane functions.
22. Have pupils look at the That's Cool' feature on Textbook p. 29. Elaborate that every turn of the screw helps
us to move a piece of metal through a wooden surface.
23. Have pupils turn to Textbook p. 30. Explain to pupils how gears function and use the pictures of the
correction tape dispenser and the bicycle to show how gears are used.
24. Have pupils think about the 'Explore' question on Textbook p. 30. Discuss possible answers. (The egg-beater
is made up of gears and a wheel and axle. The egg-beater uses gears to change the direction of the force
applied. Its spinning handle uses a wheel and axle to multiply the force applied to produce a greater force to
beat eggs and flour batter.)

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Elaborate (4th E) Application to the real world (90 min)

Purposes: To apply knowledge about the different types of simple machines and their functions and
precautionary measures to take when using simple machines
Resources: Textbook, Activity Book, a doorknob per group

1. Have pupils complete Activity 14.1 on Activity Book pp. 13—14.

2. Discuss the answers to Activity 14.1.
3. Have pupils complete Activity 14.2 on Activity Book p. 15.
4. Discuss the answers to Activity 14.2.
5. Have pupils complete Activity 14.3 on Activity Book pp. 16—17.
6. Discuss the answers to Activity 14.3.
7. Have pupils complete Activity 14.4 on Activity Book pp. 18—19.
8. Discuss the answers to Activity 14.4.
9. Have pupils complete Activity 14.5 on Activity Book pp. 20—21.
10. Discuss the answers to Activity 14.5.
11. Have pupils complete Activity 14.6 on Activity Book pp. 22—23.
12. Discuss the answers to Activity 14.6.
13. Have pupils turn to Activity 14.7 on Activity Book p. 24. Explain that the wheel of a doorknob is able to
multiply its force to move the load at its axle.
14. Have pupils complete Activity 14.7 on Activity Book pp. 24—25.
15. Discuss the answers to Activity 14.7.
16. Have pupils complete Activity 14.8 on Activity Book pp. 26—27.
17. Discuss the answers to Activity 14.8.
18. Have pupils complete Activity 14.9 on Activity Book pp. 28—29.
19. Discuss the answers to Activity 14.9.
20. Have pupils turn to Textbook p. 31. Explain some precautionary measures to take when using simple
machines.
21. Have pupils think about the 'Explore1 questions on Textbook p. 31. Discuss possible answers. (The
screwdriver is a wheel and axle. The daw hammer is a first-class lever. We should not leave the sharp edge of
the screwdriver's metal shaft and the claw hammer exposed. Accept other possible answers.}

Evaluate (5th E) Assessment (15 min)

Purpose: To assess pupils' understanding of the lesson

Resource: Textbook

1. Ask pupils the key inquiry questions for Section 14.1, Section 14.2, Section 14.3, Section 14.4, Section 14.5,
Section 14.6 and Section 14.7 again. (The five types of simple machines are the lever, pulley, wheel and axle,
inclined plane and gears. Levers help to lift or move a load. When we move the fulcrum closer to the load
or apply the force or effort further from the fulcrum, we can reduce the effort needed. Pulleys help to lift an
object. Fixed pulleys change the direction of a force and movable pulleys reduce the effort needed to lift a
load. Pulley systems are commonly used on ships and consist of both fixed and movable pulleys. The wheel
is larger than the axle and multiplies the force applied to move a load at the axle. An inclined plane helps to
reduce the effort needed to lift or move an object up a particular height. Gears are wheels with teeth. When
two or more gears interlock, they help to change the direction of the force applied or to multiply the speed
of the force applied. We need to ensure that pulleys are secure and can withstand the load applied to them.
We should also use levers that will not bend or break easily. We need to be careful when we handle simple
machines with sharp edges.}
2. Co through the'Quick Check' questions on Textbook p. 21 and p. 23. (The three parts of a lever are the load,
fulcrum and effort. Refer to labels in the magenta layer.)

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines

Lesson 2 How an aeroplane works Duration of lesson: 1 period

Learning objective
• Explain how an aeroplane as a complex machine, can do work more easily and faster.

Engage (1st E) Use of an interesting video or pictures (5 min)

Option 1
Purpose: To engage pupils and evaluate their prior knowledge about an aeroplane
Resource: A video showing an aeroplane taking off

1. Visit the website http://www.istockphoto.com/stock-video-8844443-passenger-jet-take-off.php and

show pupils a video of an aeroplane taking off. Ask:
• Why is an aeroplane called a complex machine? (This is because an aeroplane consists of many simple
machines in order to function.')

Option 2
Purpose: To engage pupils and evaluate their prior knowledge about aeroplanes
Resources: Pictures of aeroplanes landing or taking off

1. Print out the pictures of aeroplanes from http://home.comcast.net/""b.learn/cool_landings.htm and show

pupils the pictures.
2. Tell pupils that an aeroplane is a complex machine that consists of many simple machines.

Explore (2nd E) Guided inquiry (5 min)

Purpose: To introduce how an aeroplane works as a complex machine

Resource: Textbook

1. Ask pupils the key inquiry question for Section 14.8 on Textbook p. 32. Discuss possible answers.

Explain (3rd E) Teacher-directed discussion (10 min)

Purpose: To explain how an aeroplane works as a complex machine

Resource: Textbook

1. Have pupils look at the picture on Textbook pp. 32—33. Explain how an aeroplane helps us to do work. Also
explain the parts of an aeroplane and their functions.
2. Have pupils look at the That's Cool' feature on Textbook p. 33. Elaborate that the Wright brothers built the
aircraft, the Flyer, based on their experience in testing gliders. The pilot of this first flight steered the aircraft
by lying on his stomach and moving a cradle attached to his hips.

Elaborate (4th E) Application to the real world (10 min)

Purposes: To apply knowledge of how an aeroplane and other aircrafts work as complex machines
Resource: Textbook

1. Have pupils think about the 'Explore' questions on Textbook p. 32. Discuss possible answers. (Birds fly in the
sky by flapping their wings. A bird's legs are similar to an aeroplane's wheels. The difference between a bird
and an aeroplane is that an aeroplane relies on fuels in order to fly but a bird does not. Accept other possible
answers.)
2. Have pupils think about the 'Explore' question on Textbook p. 33. Discuss possible answers. (The helicopter
has many gears that help to turn its blades at an extremely fast rate so that it can fly in the sky. Accept other
possible answers.)

Evaluate (5th E) Assessment (10 min)

Purpose: To assess pupils' understanding of the lesson

Resource: Textbook

1. Ask pupils the key inquiry question for Section 14.8 again. (An aeroplane consists of many simple machines
in order to function.)
2. Go through the 'Quick Check' question on Textbook p. 33. (The parts of an aeroplane are the wheels,
engines, wings as well as the rudders and flaps on the tail and wings. The wheels allow the aeroplane to land,
take off and move on the ground. The engines provide the force for the aeroplane to move forward. The
wings provide the upthrust to keep the aeroplane in the air. The rudders and flaps on the tail and wings allow
the pilot to change the direction of the aeroplane's movements.')
3. Summarise the unit by going through the concept map in 'At a glance' on Textbook p. 34. Ensure that pupils
have understood the unit by going through the 'Self-check' activity on Textbook p. 35.

Unit 14 i 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Backaround information for teachers
Thousands of years ago, people used stones, bones and logs to help them do work. When we look at the
pyramids of Egypt and the Great Wall of China, we marvel at the inventiveness of the ancient people who
could build huge monuments without the use of modern machinery.

The Greek philosopher, Archimedes came up with the concept of simple machines at around 300 B.C. In
1600, the Italian scientist, Galileo Galilei became the first to understand that simple machines do not create
energy but only transform it from one form to another. He came up with the comprehensive theory of
simple machines.

Today, we can easily find simple machines around us. Some machines are so simple that we do not always
realise that they are actually machines that help us to do work. For example, the spoon and scissors are
simple machines which can be used to open the lid of a tin and cut things respectively.

Simple machines
• What are the types of simple machines?
Let's find out: • How do simple machines help to make work easier and faster?
• What are the safety measures to take when using simple machines?
• How does an aeroplane work?

The scissors work by multiplying

the force applied when we exert
our hand to move two sharp edges
or blades to cut things.

A pair of scissors is useful for cutting things such as cloth,

paper and even our hair. It is a lever.
How does the scissors work?
What type of machine is it? -< Other machines multiply speed
How do other machines help us to do work? •« or change the direction of a force.
They can also reduce the effort
Simple
needed to do work.

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 Background information for teachers
We say that there is work done when a force exerted on an object causes it to move. Thus, the formula to
calculate the amount of work done is the force applied or effort multiplied by the distance that the object
moves. The amount of work done is measured in joules (j), which is also used to measure energy. When we
say that a simple or complex machine makes it easier for us to do work, we mean that it needs less force to
do the same amount of work.

Simple machines allow us to increase the distance over which a smaller force is applied. We can also
change the direction of the force applied. The function of a simple machine is also known as its mechanical
advantage. In physics and engineering, mechanical advantage can be calculated using the ratio of the load
to the force applied or effort. The function or the mechanical advantage of a simple machine is sometimes
referred to as its efficiency.

Common misconception
Misconception: Machines reduce the amount of work that we do.
Actual fact: Machines do not reduce the amount of work that we do but they can make it easier or
faster for us to do the same amount of work.

The muscles work together in 14.1 Types of simple machines

groups, contracting and relaxing to
move the arm.
Our skeletal and muscular
systems must work together
for us to move and do work.
r What are the different types of simple machines?
t
Our muscles help us to do work by providing the forces
needed. The force we apply to do work is called the
load
Key inquiry question: effort. The object the effort moves or overcomes is called
The five types of simple machines the load.
are the lever, pulley, wheel and We cannot lift a load if it is too heavy. We need machines
axle, inclined plane and gears. to help us. Machines make work easier and faster to do.
However, it does not reduce the amount of work that we
actually do.

Machines can be big or small, simple or complex. A simple

machine generally has only one moving part.

When we put simple machines together, they become

a complex machine. An areoplane is an example of a
complex machine made up of many simple machines.
The muscles in our arm are similar £xpi0re Types of simple machines include the lever, pulley, wheel
to the parts of a lever. The elbow and axle, inclined plane and gears.
Compare, Infer,
joint is the fulcrum, the force Communicate
applied by the muscles is the Hold an object in your
Simple machines make work easier by performing one or
hand. Bend your arm more of the following functions:
effort and the object we hold in and move the object up
our hand is the load. Accept other and down. How do your • Multiplying force.
possible answers. muscles move an object • Multiplying speed.
when compared to simple
machines? Discuss.
• Changing the direction.

lever

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 •ground i
Ancient Egyptians used levers to move huge rocks that weighed more than 100 tonnes. Generally, a lever
is a beam or bar that turns against a fulcrum or pivot point. The three types of levers are first-class,
second-class and third-class levers. There are three parts in a lever, namely, the load, fulcrum and effort.
How easily a lever is able to lift a load depends on the distance moved by the effort. When an effort moves
a greater distance than a load, less effort is needed to lift the load.

Reinforcement for struggling learners

Have pupils investigate how a lever works to lift a load. Use a ruler as the beam of a lever and two
erasers as the fulcrum and load. Ask them to find out at which position the fulcrum should be placed so
that the force applied is greater or smaller. (When the fulcrum is placed further from the load, the force
applied is greater. When the fulcrum is placed closer to the load, the force applied is smaller.)

14.2 Levers Key inquiry question:

i Levers help to lift or move a load.
How do levers help us to do work? When we move the fulcrum closer
t to the load or apply the force or
A lever is a type of simple machine. It is a bar that is free
to turn about a fixed point. It has three parts, the load, the
effort further from the fulcrum, we
effort and the fulcrum. The point at which the lever is resting can reduce the effort needed.
is called the fulcrum. Let us look at how a lever works.

load

Parts of a lever

The effort needed to lift or move a load can be reduced by: Quick Check The three parts of a lever are the
• moving the fulcrum closer to the load. load, fulcrum and effort.
• applying the effort further from the fulcrum. What are the parts of a
lever?
However, the distance moved by the effort will be greater
than the distance moved by the load.

There are three types of levers:

• First-class levers.
• Second-class levers.
• Third-class levers.

Trebuchets are siege machines

Hundreds of years ago, that can fling up to 140 kg
during wars in the Middle of heavy objects into enemy
Ages, big rocks and fire
balls were launched using grounds. During wars in the past,
huge machines called diseased corpses were flung into
trebuchets. They helped to
hit the enemy's castle walls enemy cities using trebuchets to
or fortress. The trebuchet infect the enemy population as a
used less effort to move a
heavy load. form of biological warfare.
Simple machines 21

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 First-class and second-class levers are also called force multipliers as their function is to multiply the force
applied or effort to produce a greater force.

Reinforcement for struggling learners

Visit the website http://www.teachersdomain.org/asset/phy03_vid_moai/ and show pupils how people
in the past used levers to move huge sculptures on the Easter Island.

First-class and second-class levers

In a first-class lever, the fulcrum is between the load and
force applied (effort).
effort

Effort moves
load a greater
distance.

Load moves
a smaller
distance.

f First-class lever

In a second-class lever, the load is between the fulcrum and

the force applied (effort).

\Effortmoves
a smaller effort a greater
distance. A I distance.

Second-class lever

In both the first-class and second-class levers, the force

applied (effort) is applied as far away from the fulcrum as
possible. Thus, the effort moves a greater distance than the
load. However, the effort needed to move the load is smaller
than the load itself

The function of first-class and second-class levers is to

When we use the spoon to open —
the lid of a tin, the lid that we
Explf re multiply the force applied (effort) to produce a greater force.
This makes it easier for us to do work.
Analyse
lift is the load, the force applied The spoon is also a first- A claw hammer, a crowbar and a pair of scissors are
by our hand is the effort and the class lever. Identify the load, some examples of first-class levers. A wheelbarrow, a
effort and fulcrum for this
point at which the spoon is resting lever when we use a spoon.
bottle-opener and a nutcracker are some examples of
is the fulcrum. second-class levers.

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Enrichment for advanced learners
Some levers such as the scissors and nutcrackers are also double levers. Ask:
• What are double levers? (Double levers are made up of two levers having the same fulcrum. They have
two efforts and two loads but only one fulcrum.)

Reinforcement for struggling learners

Have pupils visit the website http://www.edheads.org/activities/simple-machines/framejoader.htm
and play an interactive game to visualise and identify the parts of different types of levers.

Refer to labels in the magenta layer.

Identify the effort, fulcrum
and load for each lever.

t A wheelbarrow, a bottle-opener
and a nutcracker ore examples
of second-class levers.

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines

 Background information for teachers
Third-class levers are also known as movement multipliers because they multiply the speed of the force
applied or effort so that work is done faster.

Enrichment for advanced learners

• Have pupils list other examples of third-class levers. (Baseball bat and tweezers. Accept other
possible answers.)

Third-class levers
In a third-class lever, the force applied (effort) is between the
load and fulcrum.

i i
geater effort i i
Load moves
Effort moves a |oad 1 a greater
smaller distance. . / distance.

f Third-class lever

The function of third-class levers is to multiply the speed of

the force applied (effortl so that work is done faster. However,
a greater effort is needed to move the load.

A fishing rod, a pair of tongs and a broom are some examples

t Fishing rod
of third class-levers.

greater effort greater effort

greater effort
small distance
moved by effort
small distance
moved by effort

A pair of tongs Broom

Unlike other types of levers, the -

effort is applied between the
Exptore
Observe, Compare, Analyse
load and fulcrum in a third-class What are the differences between third-class levers and other
lever. Its function is to multiply types of levers?
the speed of the force applied or
effort. This effort may be greater
than the load.

14.10 Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Backgro-
A pulley is also called a sheave or a drum. A pulley consists of a wheel that may have a grooved rim. A rope,
cable, belt or chain normally runs over the wheel. Fixed pulleys change the direction of the force applied or
effort. Movable pulleys reduce the force applied or effort.

Key inquiry question:

Pulleys help to lift an object. Fixed
pulleys change the direction of a
14.3 Pulleys force and movable pulleys reduce
How do pulleys help us to do work? the effort needed to lift a load.
Pulley systems are commonly used
The pulley is a type of simple machine. It can help us to
It has a wheel on ships and consist of both fixed
lift an object. Let us look at how it works. that rotates freely. and movable pulleys.
There are three types of pulleys:
• fixed pulleys.
• movable pulleys. The object is tied to
• pulley systems. a rope that winds
around the wheel.
Fixed pulleys t Pulley
When we pull on the rope downwards, the effort moves
downwards while the load moves upwards. When the pulley
is fixed to a support, it is called a fixed pulley.

J effort moved
downwards
distance moved
by effort

distance moved
The effort and
— load moved the
same distance.

by load

^ A fixed pulley changes the direction of the force applied (effort)

The function of a fixed pulley is to change the direction of the

force applied (effort). However, the pulley does not reduce
the effort needed to lift the load. This is because the load
and effort move the same distance.

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.11
 Reinforcement for struggling learners
Have pupils visit the website http://www.technologystudent.com/gears1/pulley7.htm to help them
understand how pulleys work.

Movable pulley
When the pulley is not fixed to any support, it is called a
movable pulley. This is because it moves together with the
load.

distance
moved by
effort

The effort
moved
a greater
distance than
the load.

+ A movable pulley moves together with the load.

When a movable pulley is used, the effort and load move

in the same direction. The function of a movable pulley is to
reduce the force applied (effortl. This is because the effort
moves a greater distance than the load.

Using the movable pulley makes

pulling the boat to the shore easier.

14.12 Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Backaround information for teachers
Pulley systems use both fixed and movable pulleys with a rope or cable threaded between them and are
used to lift or pull heavy loads. Pulley systems are more commonly found on boats and sailing ships and
they are also known as a block and tackle. A block is a series of pulleys mounted together. When a rope or
cable runs through a block or series of blocks, it is referred to as a tackle. The most common arrangement of
a block and tackle is to have one block attached to a fixed position and another block which moves with the
load when it is being lifted or pulled.

Pulley systems
A pulley system is made up of more than one pulley to lift a
load. They are made up of fixed pulleys and movable pulleys.

|— fixed pulley
fixed
pulleys
movable
pulley
movable
pulleys

The function of a pulley system is to multiply the force applied

(effort) to produce a greater force to lift the load. This makes
• Leonardo da Vinci also came up
it easier for us to do work. The famous Italian painter, with the ideas for helicopters,
Leonardo da Vinci was tanks and calculators before these
Pulley systems are commonly used on ships. This type of also a great designer
of machines. He drew machines were actually invented.
pulley system is usually called a block and tackle.
many scientific diagrams
including sketches of
pulleys.

Expifre One type of pulley that is

commonly found in schools is on
Observe, Communicate
Look around you and find the flag pole that raises the flag.
pulleys. Which type of It is usually a fixed pulley. Accept
pulley are they? List them.
other possible answers.
4- A block and taclde is used on
a fishing boat to lift fishJftg
;ts and other equipment.

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines

 A common example of how a wheel and axle was used in the past is the design of wells back in the 19th
century. This involves a wheel that is turned in order to move the connected axle and the rope to which a
pail is attached. The rope for the pail is wound around the axle. For this design, the force can be applied
either at the axle or the wheel.

Key inquiry question: 14.4 Wheel and axle

The wheel is larger than the axle
and multiplies the force applied to How does a wheel and axle help us to do work?
move a load at the axle. A wheel and axle is a type of simple machine. A doorknob
is an example of a wheel and axle. It is made up of a
wheel fixed to a rod called the axle. If a door did not have a
doorknob, we would need a lot of effort to open a door.

axfe wheel The wheel is bigger than the axle. When the wheel turns, the
axle turns too. The wheel moves a greater distance than the
t Doorknob axle. Thus, we exert less effort at the wheel.

The function of a wheel and axle is to multiply the force

applied (effort) to produce a greater force. The wheel
multiplies the force applied to move a load at the axle.
The original Ferris wheel was
designed and constructed by A water tap and hand drill are examples of a wheel and
Have you taken a ride
George Washington Gale Ferris on a Ferris wheel in an axle.
junior in 1893 for an exposition in amusement park? The
Ferris wheel works as a
Chicago, United States. The term wheel and axle.The force
'Ferris wheel' later became known applied (effort) on its axle
wheel
ailows the wheel to spin.
for all such structures.

axle

A screwdriver is a wheel and axle.

The handle of the screwdriver is
Expifre
Observe,
the wheel and the metal shaft Communicate, Analyse
or rod is the axle. Accept other • Find other simple
machines that have a
possible answers. wheel and axle.
• List them.
• Identify the wheel and

Unit 14 > 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Backoround information for teachers
An inclined plane is a flat surface that allows us to move objects to reach a higher level with less effort. A
wedge consists of two inclined planes combined together to form a triangular-shaped tool. It was commonly
used to split wood in ancient times. A blade also consists of two inclined planes but is positioned so that the
planes meet at one edge. Knives and chisels are examples of blades.

Reinforcement for struggling learners

Have pupils visit the website http://en.wikipedia.org/wiki/Egyptian_pyramid_construction_techniques
to help them understand how ancient Egyptians designed ramps to move heavy loads when they built
the pyramids.

Key inquiry question:

An inclined plane helps to reduce
14.5 Inclined plane That s
* CQ©U- the effort needed to lift or move
an object up a particular height.
Did you know that the
How does an inclined plane help us to do work? thread of a screw is an
inclined plane? It is smiliar
An inclined plane is another type of simple machine. Less to a slope that wraps
effort is needed if we use an inclined plane to reach a higher around the screw. It helps • Every turn of the screw helps us to
level. Also, it is easier to pull or push a load up an inclined the screw to sink into the
wood easily as the screw is move a piece of metal through a
plane. turned. wooden surface.
The function of an inclined plane is to reduce the force
applied (effort). This is because the effort moves the objects
gf thread
over a greater distance.
wood
A ramp and a staircase are another examples of inclined planes.

«• Screw

2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.15
 Background information for teachers
The earliest record of gears being mentioned was in 50 A.D by the Greek mathematician, Hero of Alexandria
but the idea of gears can be traced back to Archimedes in 300 B.C. Gears are essentially a rotating simple
machine with teeth on their wheels.

Two or more gears have to fit into one another in order for them to work together. When we turn one gear,
the gear next to it turns too. However, both gears turn in opposite directions. For example, when one bigger
gear turns in an anti-clockwise direction, the smaller gear turns in a clockwise direction. Also, when the
bigger gear turns one round, the smaller gear turns more than one round. This means that the smaller gear
turns faster. On the other hand, when the smaller gear turns one round, the bigger gear turns less than one
round. This means that the bigger gear turns more slowly.

14.6 Gears
Key inquiry question:
Gears are wheels with teeth. When
-> How do gears help us to do work? t
two or more gears interlock, they Gears are another type of simple machine. Gears are wheels
with teeth on them. Let us see how gears work.
help to change the direction of the
force applied or to multiply the 1When two or more
gears interlock, they ' Gears that are next to
speed of the force applied. turn together. clockwise ' each other turn in opposite
anti-clockwise
directions. In this way, gears
change the direction of the
force applied (effort).

When the bigger gear

turns in an anti-clockwise
The egg-beater is made up of
gears and a wheel and axle. The
Explore Two interlocking gears in
a correction tape dispenser
direction, the smaller
gear turns in a clockwise
Infer, Communicate direction.
egg-beater uses gears to change Identify the types of simple
the direction of the force applied. machines in an egg-beater. The function of gears is to change the direction of the force
How does each of them help
Its spinning handle uses a wheel the egg-beater to work?
applied (effort). Gears also multiply the speed of the force
and axle to multiply the force Discuss. applied (effort).
applied to produce a greater force Gears can be found in objects such as a correction tape
to beat eggs and flour batter. dispenser and a bicycle.

The gears are

connected by a chain.

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

14.7 Precautionary measures in using
simple machines •Key inquiry question:
We need to ensure that pulleys are
What precautionary measures can we take secure and can withstand the load
when using simple machines?
applied to them. We should also
We need to be careful and keep ourselves safe when we use use levers that will not bend or
simple machines to do work. Here are some precautionary pulley break easily. We need to be careful
measures to take when using simple machines. when we handle simple machines
with sharp edges.

Use the right type of simple Secure pulleys properly

machines for the right job. before using then and
Lifting heavy things with a ensure that the support for
lever that can bend and break the pulleys can withstand the
easily may cause injury. load you are lifting.

Simple machines that are

Explfre • The screwdriver is a wheel and
axle. The claw hammer is a
sharp should be handled Observe, Investigate
with care. Always cover the What types of simple first-class lever. We should not
sharp edges when storing machines can you find in leave the sharp edge of the
or transporting them. Do not your home? What
precautions do you need to screwdriver's metal shaft and the
leave sharp edges exposed. take when using them? claw hammer exposed. Accept
other possible answers.

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.17
 Background information for teachers
Aeroplanes and other aircrafts have greatly benefited Man. Currently, large numbers of people are able to
travel around the world on these aircrafts, which have resulted in increasing tourism and trade. Cargo and
goods can also be transported over long distances.

14.8 How an aeroplane works

Key inquiry question:
An aeroplane consists of many
->- How does an aeroplane work as a complex machine?
f
The aeroplane is one of Man's greatest inventions. An
simple machines in order to
aeroplane is a complex machine because it requires several
function. simple machines working together in order for it to fly in the
sky and operate successfully.

Aeroplanes are able to travel at much faster speeds by

flying in the sky in comparison to motor vehicles travelling
on roads. An aeroplane can also carry heavy loads. Today,
many people travel between countries by aeroplane and
this complex machine is also used to transport cargo and
mail.

Parts of an aeroplane
Here are the different parts of the aeroplane and
their functions.

Birds fly in the sky by flapping

their wings.
Explore, Compare,
A bird's legs are similar to an Infer
aeroplane's wheels. The difference Birds can fly in the sky.
Look at some birds flying Wheels
between a bird and an aeroplane is and landing. How are The wheels allow the
that an aeroplane relies on burning they able to move? What aeroplane to land, take off
are the similarities and and move on the ground.
fuels in order to fly but a bird does differences between a
not. Accept other possible answers. bird and an aeroplane?

Engines
The engines provide
the force to move the
aeroplane forward.

Unit 14 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Reinforcement for struggling learners
• Have pupils visit the website http://inventionatplay.org/playhousejinker.html and play the game to help
them understand that complex machines are made up of many simple machines.

Exptore The helicopter has many gears

that help to turn its blades at
Analyse, Communicate
The helicopter is another complex an extremely fast rate so that it
machine that flies in the sky. What can fly in the sky. Accept other
are the simple machines that help it to
function? Discuss. possible answers.

Wings
The wings are shaped uniquely to
provide the upthrust, which is an
upward force, to keep the aeroplane
in the air.
Tail and wings
The rudders and flaps on the
tail and wings allow the pilot
to change the direction of the
aeroplane's movements.

•The Wright brothers built the

aircraft, the Flyer, based on their
experience in testing gliders. The
pilot of this first flight steered the
aircraft by lying on his stomach
and moving a cradle attached to
his hips.

•The parts of an aeroplane are the

the wheels, engines, wings as
well as the rudders and flaps on
the tail and wings. The wheels
The first successfully powered allow the aeroplane to land, take
flight flown by Man took place on
17 December 1903 in Kitty Hawk, off and move on the ground.
United States. The aircraft, named The engines provide the force for
the Flyer, was built by two brothers,
Orville and Wilbur Wright.
Quick Check the aeroplane to move forward.
Today, the largest aeroplane is Name the parts of a The wings provide the upthrust
the Airbus A380. It can carry over aeroplane. List the
800 people and is able to move argely mode to keep the aeroplane in the air.
functions of each part.
faster and do work more easily of wood and could only The rudders and flaps on the
than the Flyer. carry one person.
tail and wings allow the pilot
to change the direction of the
aeroplane's movements.

i 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.19
 Multiplying speed
and changing
direction

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 1. load
2. complex
The force we apply to do work is called the effort and the object the effort moves or overcomes is 3. axle, gears
4. fulcrum, third-class
called the
5. multiply
2. Machines make work easier and faster to do and they can be big or small. They are made up of simple 6. third-class, multiply
machines and __ machines. 7. movable
8. direction, distance, multiply
The lever, pulley, wheel and , inclined plane and
9. axle, axle, multiply
-are types of simple machines. 10. reduces, distance
11. Gears, multiply
4. The point at which the lever is resting is called the - . There are three types
12. precautionary
of levers, the first-class, second-class and 13. complex
The first-class lever has the fulcrum between the load and force applied or effort, while the
second-class lever has the load between the fulcrum and the force applied or effort. Their function is to

the force applied or effort to produce a greater force.

6. The- lever has the force applied or effort between the load on one end and

the fulcrum on the opposite end. Its function is to the speed of the force
applied or effort.

7. There are three types of pulleys, fixed and. . pulleys and pulley systems.

8. The function of a fixed pulley is to change the. . of the force applied

or effort. The function of a movable pulley is to reduce the effort because the effort moves a greater

than the load. The function of a pulley system is to

the force applied or effort to produce a greater force to lift a load.

For the wheel and , the wheel moves a greater distance than the

.. The function of this simple machine is to the

force applied or effort.

10 The inclined plane . - the force applied because the effort moves the load

over a greater

11. -are wheels with teeth. Their function is to change the direction of the

force applied or effort and to . - the force applied or effort.

12. We need to be careful and take - — measures when using simple machines
so that we will not get hurt.

13. An aeroplane is a 1 machine because it requires several simple machines

working together in order for it to operate successfully.

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.21
 . . 1 ^^Bl^
More Science words • ^^HM^£ ^^Vr/ v^ici
Sripnrp filnccnrv
i^c vjiwjjui y 1^^^^^^^H

• Mechanical advantage : Block and tackle : Pulley system used on Load : Object that moves
a ship
Number of times a machine Movable pulleys : Pulleys that moves with
Cargo : Goods transported by air the load
multiplies a force or or sea
effort applied Complex machine : Consists of many simple
Pulley : Type of simple machine
consisting of a wheel that
machines
• Sheave : Mechanism rotates freely to lift objects
Effort : Force we apply
consisting of a wheel on Pulley systems : Consist of fixed and
First-class levers : Type of lever having the movable pulleys
an axle
fulcrum between the load Rudders : Movable parts of an
• Wedge : Combination of two I a n d effort applied aeroplane's tail
inclined planes Fixed pulleys : Pulleys attached Second-class levers : Type of lever having the load
permanently to a support between the fulcrum and the
Flaps : Brood, flat sections along effort applied
the edge of an aeroplane's Simple machine : Object that helps to make
wings work easier or faster and
j consists of only one moving
Fulcrum : Point at which the part
lever rests
Third-class levers Type of lever having the
Gears Type of simple machine effort applied between the
that are wheels with teeth load on one end and the
on them fulcrum on the opposite end
Inclined plane Type of simple machine Upthrust Upward force that keep
that allows us to reach a something in the air
higher level with less effort
Wheel and axle Type of simple machine
Lever Type of simple machine consisting of a wheel fixed to
consisting of a bar and a rod called the axle
fulcrum used to multiply
force or speed to move
another object.

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Before you carry out
the activity
Pupils should have been taught
Activity 14.1 Simple machines
• The five types of simple
machines are the lever, pulley,
Process skill
wheel and axle, inclined plane
Communicate : the knowledge of the different types of simple machines and gears.
• Simple machines function by
multiplying force, multiplying
JAim: To recognise the different types of simple machines and their functions
speed and changing the
direction of a force.
Answer the following questions.

1. How does a simple machine help us to do work?

Notes on answers
It makes it easier and faster for us to do work.
Have pupils refer to Textbook
2. What are the types of simple machines? List them below. p. 20 if they are unable to
answer the questions.
Levers
Inclined plane

Wheel and axle

Pulleys

Gears
/ (Accept other possible answers.)

Simple machines 13

> 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.23
 Notes on answers
• Guide pupils to complete the
diagram and explain that the 3. Complete the diagram below by filling in the labels in the boxes provided. Then
load is the object we move complete the sentences that follow.
and the effort is the force we
apply to do work.

The force we apply to do work is called effort . The object we lift or try

to move is called the kxid . simple machines make work easier by

performing one or more functions. These functions are multiplying force

multiplying speed and changing the direction of a force.

14 Unit 14

14.24 Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Reinforcement for struggling learners
Explain to pupils that the load, fulcrum and effort are basic parts that exist for all types of levers.

Before you carry out

the activity
Pupils should have been taught
Activity 14.2 How levers work
• The parts of a lever include the
load, effort and fulcrum.
Process skill
• The three different types of
Communicate : the knowledge of levers and how they work in a diagram levers include the first-class,
second-class and third-class
levers.
I Aim: To recognise how levers work

1. The diagram below shows a lever. Complete the diagram by filling in the labels in the
boxes provided. Then answer questions that follow.
Notes on answers
Have pupils refer to Textbook
p. 21 if they are unable to
answer the questions.

2. What is a fulcrum in a lever?

The point at which the lever is resting

3. What are the three types of levers?

First-class lever, second-class lever and third-class lever

Simple machines 15

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.25
 Enrichment for advanced learners
Have the pupils compare the distance the effort moved, to the distance the load moved and how it affects
the force applied or effort. (The effort moved over a greater distance than the load. This reduced the force
applied or effort.)

Before you carry out

the activity
Pupils should have been taught
Activity 14.3 Reducing effort
• There are two ways to reduce
the effort when using a lever
to lift a load. We must move Process skills
the fulcrum closer to the load Communicate : the knowledge of how effort can be reduced when lifting a load with
and apply the effort further a lever in diagrams
from the fulcrum. Infer : the two ways to reduce effort in lifting a load with a lever

J A i m : To understand the two ways to reduce effort in lifting a load with a lever

There are two ways to reduce our effort when we lift or move a load. The following
diagrams show how this is done. Look at the diagrams, then answer the questions.

When a load cannot be lifted First way to lift a load

load

distance between fulcrum and load distance between fulcrum and load

Diagram A Diagram B

1. (a) What was done to enable the load to be lifted in Diagram B?

The fulcrum was moved closer to the load.

(b| What can we conclude about this first way to reduce the effort to lift the load?

The effort to lift the load is reduced when the fulcrum is placed closer to the load.

16 Unit 14

14.26 Unit 14 ) 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Reinforcement for struggling learners
• Have pupils visit the website http://www.teachersdomain.org/asset/wnet09_vid_wnetlever/ to
understand how to reduce the effort when using levers.

Notes on answers
• Guide pupils to conclude that
Second way to lift a load
the effort needed to lift a load
When a load cannot be lifted
with a lever can be reduced
when the fulcrum is placed
closer to the load. When a
longer lever is used, the effort
is applied further away from
load the fulcrum and this also
reduces the effort needed to
lift the load.
distance between fulcrum and load distance between fulcrum and load

Diagram C Diagram D

2. (a) What was done to enable the load to be lifted in Diagram D?

A longer lever was used to lift the load.

(b) What can we conclude about this second way to reduce the effort to lift the load?

The effort to lift the load is reduced when a longer lever is used.

Simple machines 17

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.27
Before you carry out
the activity
Pupils should have been taught
• There are three types of levers
Activity 14.4 Types of levers
namely, first-class, second-class
and third-class levers. Process skills

• A claw hammer, a crowbar and Communicate : the knowledge of the different types of levers
a pair of scissors are examples Analyse : a picture and identify the type of lever it shows
of first-class levers.
• A wheelbarrow, a bottle-opener
| Aim: To identify the different types of levers
and a nutcracker are examples
of second-class levers.
• A fishing rod, a pair of tongs 1. Look at each picture below and identify the type of lever it is. Then answer the question.

and a broom are examples of Type of lever

third-class levers.

First-class lever

Second-class lever

18 Unit 14

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Reinforcement for struggling learners
• Have pupils visit the website http://www.technologystudent.com/forcmom/lever1.htm to help them
visualise how the different types of levers function.

Notes on answers
Remind pupils that the
Type of lever function of both a first-class
and second-class lever is to
multiply force. The function of
a third-class lever is to multiply
speed.
Have pupils refer to Textbook
pp. 22-24 if they have
difficulty completing this
activity.

2. What is the function of each type of lever?

First-class lever: To multiply force

Second-class lever: To multiply force

Third-class lever: To multiply speed

Simple machines 19

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.29
 Before you carry out
the activity
Pupils should have been taught
• A nutcracker is an example of
Activity 14.5 Nutcracker
a second-class lever.
Process skills
• In a second-class lever, the
load is between the fulcrum Infer : that a lever such as a nutcracker reduces our effort to crack a walnut
and the force applied or effort. Analyse : how the nutcracker cracks a walnut by multiplying force
Predict : the position at which the walnut will crack most easily

J Aim: To analyse how a lever such as a nutcracker reduces our effort to crack a walnut
by multiplying the force applied

Look at the picture. Then use it to answer the following questions.

fulcrum

1. At which position. A, B or C will the least force be needed to crack the walnut
most easily?

2. Where is the fulcrum of the nutcracker? Circle the position of the fulcrum and label it in
the picture.

3. At which position would the effort applied be, for it to move the greatest distance to
crack the walnut?

20 Unit 14

14.30 Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Enrichment for advanced learners
• Have pupils find out and name some other examples of second-class levers and share their findings with
the class. (Other examples of second-class levers include a stapler and a hole-puncher. Accept other
possible answers.)

Notes on answers
Explain to pupils that in
4. What type of lever is the nutcracker? second-class levers, the effort
A second-class lever is applied as far away from the
fulcrum as possible.
5. How does the nutcracker make it easier for us to do work?

The nutcracker reduces the effort needed to crack a nut by multiplying the force

applied.

6. How does applying the effort further from the fulcrum affect the effort needed to crack
a nut?

The further the effort is from the fulcrum, the lesser the effort needed to crack a nut.

Simple machines 21

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.31
 Reinforcement for struggling learners
• Have pupils visit the website http://video.google.com/videoplay?docid=-1387384954011819873&hl=en
&emb=1# and watch a video to help them visualise how pulleys are used to lift loads.

Before you carry out

the activity
Pupils should have been taught
Activity 14.6 Types of pulleys
• The three different types
of pulleys are fixed pulleys,
Process skill
movable pulleys and
pulley systems. Communicate : the knowledge of the function of each different type of pulley
• A fixed pulley's function is
to change the direction of
the force applied or effort. A JAim: To identify the function of each different type of pulley
movable pulley's function is to
reduce the effort because the 1. Look at each picture. Identify the function of each type of pulley. Then complete
effort moves a greater distance the sentences.
than the load. A pulley
Type of pulley Function
system's function is to multiply
the force applied or effort to
produce a greater force to lift
a load.
• The type of pulley used on a
ship is a pulley system, which To change the direction of the force
is usually called a block and applied (effort)
tackle.

To reduce the effort needed to move

a load

22 Unit 14

14.32 Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Notes on answers
Explain to pupils that a fixed
Function pulley is fixed to a support
while a movable pulley is not.
Pulley systems are commonly
found on boats and ships.
Have pupils refer to Textbook
pp. 25-27 if they have difficulty
Multiplying the force applied (effort)
completing this activity.

The three . types of pulleys are the. fixed . pulley,

movable pulley and pulley system. A pulley system used on a ship is

tackle
usually called a block and

Simple machines 23

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines 14.33
Reinforcement for struggling learners
Draw two circles, one bigger than the other on the board and explain to pupils that the bigger circle
represents the wheel and the smaller circle represents the axle. Show pupils that the bigger wheel travels
a greater distance than the axle for the same number of turns made by the wheels.

Before you carry out

the activity
Pupils should have been taught
Activity 14.7 Wheel and axle
• The function of a wheel
and axle is to multiply the
Process skills
force applied.
• A water tap and hand drill are Observe : how the doorknob turns and helps us to open a door easily
some examples of a wheel and Infer : that the wheel of a doorknob is able to multiply its force to move the load at
the axle
axle.
Investigate : how a doorknob works as a wheel and axle to open the door

Where to obtain or buy

the materials Aim: To observe how the wheel and axle of a doorknob multipy the force applied
• Doorknobs can be found
in the classroom or the
Science laboratory in school.

1. Work in groups. Turn the doorknob of the door

Tips and time-savers in your classroom or Science laboratory.
axle
2. Observe the distance moved by the wheel and
• Increase the number of pupils wheel
the axle when the doorknob is turned.
in each group if there are not
enough doorknobs available. 3. Draw the doorknob in the space provided.

4. Label the wheel and the axle of the doorknob.

Safety precautions
Ensure that the pupils do not
close the door on their fingers.

Doorknob

1. Where do you apply an effort to open the door?

At the doorknob

2. Which moved a greater distance, the wheel or the axle?

The wheel

24 Unit 14

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Enrichment for advanced learners
• What are two other examples of a wheel and axle? (Pencil sharpener and bicycle wheels. Accept other
possible answers.)

Notes on observations
and results
Guide pupils to conclude that
the wheel moves a greater
1. Which is bigger, the wheel or the axle?
distance than the axle.
The wheel

2. What happens to the axle when you turn the wheel of the doorknob?

When the wheel turns, the axle also turns

3. How does the wheel of the doorknob multiply its force?

The wheel moves a greater distance than the axle. So, less effort is exerted at the

wheel than at the axle. In this way, the wheel is able to multiply its force applied to

move a load at the axle.

A wheel and axle is a simple machine. The wheel is. bigger . than the axle.
greater
When the wheel turns, the axle will also turn. The wheel moves a.
multiplies . the force applied to move the
distance than the axle. The wheel.
load at the axle.

Simple machines 25

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines

Enrichment for advanced learners
• Have pupils create their own word puzzles using some of the terms such as Never' and 'fulcrum' that they
have learnt in this unit.

Before you carry out I

the activity I
Pupils should have been taught
Activity 14.8 Inclined planes
• An inclined plane is a simple
machine which allows us to •^•^^••^^H
Process skill
use a smaller ettort to push
LL L

or pull a load up to reach a Communicate : the knowledge of inclined planes in a word puzzle
higher level.
• Some examples of inclined
planes are a ramp, a staircase [ Aim : To recognise and understand inclined planes

and a screw. f
Use the clues on the next page to find the missing words in the word puzzle below. Then
circle the words.

V Q C I V S U 0 Z S E V X

M L F N L B V X W 0 S M X

S H R C D Z W V W I A A A

G G N L P J Z R B Q C D X

Z Y U I L C 0 E Q Q R I A

T P N N T T M D Y Z I S C

D A Z E R P V U C C A T B

H S M D 0 U B C C L T A V

0 D V P f S L E C C S N X

L F A L F H H J V Q E C 0

W B F A E 0 Z J S T J E P

Z
F

L
Y

H
N

E
V

A
J

U
a0
A

Z
M

N
PJ

B
B

Z
U

I
L

26 Unit 14

Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Notes on answers
Have pupils fill in the answers
CLUES to the clues in the blanks first,
1. An inclined plane ^of simp|e machjne with a sloping surface.
before attempting to circle the
js Q
words in the puzzle.
2. Less — effort . is needed if we use an inclined plane to reach a Have pupils refer to Textbook
higher level.
p. 29 if they have difficulty
3. It is easier to pull or. push . an object up an inclined plane. completing this activity.

4. The function of an inclined plane is to. reduce . the force applied

because the effort moves the object over a greater distance.

5. A_
ramp . is an example of an inclined plane which helps people on
wheelchairs to move to a higher level.

6. A staircase js another example of an inclined plane with steps.

Simple machines 27

© 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines

Before you carry out
the activity
Pupils should have been taught
Activity 14.9 Gears
• Gears are wheels with teeth
on them. They turn together
Process skills
because they interlock.
• Gears change the direction Communicate : the knowledge of gears and how they change the direction of the
of the force applied or effort force applied
Analyse : how gears turn together
and multiply the force applied
or effort.
Aim: To recognise how gears work to change the direction of the force applied

Look at the picture below. Then use it to answer the following questions.

1. The picture shows two gears. What are gears?

They are simple machines that have wheels and teeth.

28 Unit 14

Unit 14 2010 Marshall Cavendish International (Singapore) Pte Ltd

 Reinforcement for struggling learners
• Have pupils visit the website http://www.howstuffworks.com/gear.htm and watch a video to understand
how gears work.

Notes on answers
Explain to pupils that a smaller
2. What happens to the bigger gear when we turn the smaller gear? gear will turn more than one
The bigger gear will also turn but in the opposite direction. round with every turn of the
bigger gear.
3. If the smaller gear turns in a clockwise direction, in what direction will the bigger Have pupils refer to Textbook
gear turn?
p. 30 if they are unable to
Anti-clockwise direction answer the questions.

4. What makes the gears turn together?

The teeth of the gears interlocking as they turn.

5. Complete the sentences.

opposite
Gears that are next to each other will always move in.

direction
directions. Gears change the of the force applied.

Extension 1
The bigger gear has more teeth than the smaller gear. When the bigger gear turns one
round, how does it affect the smaller gear? Explain your answer.
The smaller gear will turn more than one round with every turn of the bigger gear. This

means that the smaller gear turns faster than the bigger gear. So, gears can produce

faster or slower movement depending on whether the bigger or the smaller gear is

turned first.

Simple machines 29

i 2010 Marshall Cavendish International (Singapore) Pte Ltd Simple machines

 Notes

14.40 Unit 14 © 2010 Marshall Cavendish International (Singapore) Pte Ltd