Year 4, Term 1: Simple machines
Scope and sequence: Forces, Mechanical advantage, Ratios, Torque
Learning intention: Students can identify, explain and demonstrate a variety of contact and non-contact forces.
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)
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:
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.
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: https://au.pinterest.com/pin/503629170801754769/)
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
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.
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
Simulation by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC-BY-4.0 (https://phet.colorado.edu).
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.
Wheels and axles
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.
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.
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
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.
A complex machine is a combination of two or more simple machines.
Relevant terminology (in
alphabetical order): air resistance,
contact, force, friction, gravity, non-contact.
Relationships between components: