Year 4, Term 1: Simple machines

Focus: Forces

Scope and sequence: Forces, Mechanical advantage, Ratios, Torque

Learning intention: Students can identify, explain and demonstrate a variety of contact and non-contact forces.

NSW Syllabus
Australian Curriculum (version 9.0)
"A student describes how contact and non-contact forces affect an object’s motion." (ST2-9PW-ST)
"Students learn to identify how forces can be exerted by one object on another and investigate the effect of frictional, gravitational and magnetic forces on the motion of objects." (AC9S4U03)

Week 1

Rube Goldberg machines

Introduction to simple machines

There are generally considered to be six simple machines and many of these have been in use for thousands of years.  The six simple machines are:

  1. Levers
  2. Inclined planes
  3. Wedges
  4. Screws
  5. Wheels and axles
  6. Pulleys

Ask children to write down some examples of simple machines before they watch the video (6:12).  This video provides a good overview of all six simple machines and some common applications. 

Week 2

Contact and non-contact forces

Gravity and air resistance can be taught together as air resistance affects the rate of falling bodies.  Air resistance is a type of friction.

'Twirly whirlies' provide a suitable experiment as they are readily available and can be easily modified to promote experimentation.  An A4 printable template is available here which will give you six per page.  It is recommended that each student receives three each to encourage experimentation.

(CC BY 2.0, Source:

This template has three twirly whirlies.  Children cut along the solid lines and fold along the dotted lines.  Give each child three twirly whirlies and ask them to modify each and then make predictions about how they will fall.  For example, attach a big paperclip to Part C for one and a smaller paper to Part C for another.



The following video (4:15) describes a world without friction.


This video (0:47) shows an experiment conducted on the Moon.

Anti-gravity creature


Week 3


This first video (4:46) is titled The mighty mathematics of the lever as it traces the use of levers right back to Archimedes and his boast that he could move the whole world with a gigantic lever.

Q: Do you think Archimedes was serious about lifting the whole world or was he making a point?

The following video (2:44) provides and overview of the three main classes of levers and a handy way to remember them.

This simulation is a good way to become familiar with first-class levers.  The concrete pylons are also useful for making predictions.

Simulation by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC-BY-4.0 (

Balances and unbalanced forces

The following video (2:45) explains how forces are considered to be balanced if an objects remains at rest of at a constant velocity.  This is in contrast to unbalanced forces which result in an object changing its velocity or direction.

Week 4

Wheels and axles

Week 5


This video (1:33) is a great introduction to pulleys.

Block and tackle

A block and tackle is when two or more pulleys are grouped together with a rope or cable to lift heavy loads.  The separation of the pulleys in this diagram shows the force balance that results in a rope tension of W/2.


Week 6

Inclined planes

Week 7



Week 8


Week 9

Gears and ratios

Gears are not generally considered to be one of the six simple machines but they are very common and they fit well within this unit.  This video (6:26) explains how gears work and uses important terminology such as speed and torque.


Torque can be defined as rotational force.  The following video (2:10) explains torque and uses some familiar examples with bicycles.


Ratios are comparisons.  The following scenario involves a ratio of 1:7.

Q: There were 24,000 people at a concert.  For every 7 adults there was 1 child.  How many children were at the concert?

A: 3,000 children (21,000 adults)

Power to weight ratio
The ratio between power and weight is a common consideration when dealing with the performance of an engines and motors.  This principle can even be seen in humans when competing in competitions such as Ninja Warrior.  The following video (3:13) discusses the power to weight ratio in terms of cycling.

Week 10

Complex machines

A complex machine is a combination of two or more simple machines.

Moderated self-assessment

Relevant terminology (in alphabetical order): air resistance, contact, force, friction, gravity, non-contact.

Relationships between components:

  • Gravity is a force of attraction between objects.  It is a non-contact force which is more noticeable between large objects such as planets and stars. 
  • Friction is a contact force which opposes movement between surfaces. 
  • Air resistance is a type of friction.  Air resistance is still a contact force because air contains gases and particles.

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

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