This unit can be taught in tandem with the delivery of the Let’s Ride practical sessions to address
content in the Science curriculum using a cycling-based theme.
Before undertaking the following activities, students will need to be able to:



describe the different types of contact and non-contact forces
demonstrate how pushes or pulls can make objects speed up, slow down, change
direction, or stop
explain how forces have a size and direction.
By the end of the unit of work, students will be able to:


describe how different forces can be applied in order to ride a bicycle safely and
efficiently.
conduct investigations into the forces at work when riding a bicycle .
Science
Year 4




Forces can be exerted by one object on another through direct contact or from a
distance (ACSSU076)
With guidance, identify questions in familiar contexts that can be investigated
scientifically and make predictions based on prior knowledge (ACSIS064)
With guidance, plan and conduct scientific investigations to find answers to questions,
considering the safe use of appropriate materials and equipment (ACSIS065)
Use a range of methods including tables and simple column graphs to represent data
and to identify patterns and trends (ACSIS068)





Students describe how contact and non-contact forces affect interactions between
objects.
Students follow instructions to identify investigable questions about familiar contexts
and make predictions based on prior knowledge.
Students describe ways to conduct investigations and safely use equipment to make
and record observations with accuracy.
Students use provided tables and column graphs to organise data and identify
patterns.
Students suggest explanations for observations and compare their findings with their
predictions.

Understanding forces and what makes a
bicycle move.

Students explain that forces that push and
pull can make a bike speed up, slow down
or change direction.
Students can identify the size and direction
of different forces when riding a bike.
Experimenting with force

Speeding up and slowing down –
understanding friction

Using gears to increase force and speed
Design your own bike
Students explain that friction occurs when
two surfaces touch each other.
Students describe how friction slows
moving objects down.
Students describe ways in which friction
can be increased and decreased to slow
down or speed up a bike.
Students investigate how a bicycle works, naming the parts and identifying how pushes and pulls are
involved in making it move. Use the “Parts of the bicycle template” to label the parts of the bike and
use arrows to indicate the size and direction of the forces (pushes and pulls) that make it move, stop
and change direction.
Students use a real bike on blocks to demonstrate the effect of pushing the pedal down and the
transfer of energy resulting in the forward movement of the bicycle (rotation of the rear wheel.
Students discuss how they could alter the different forces in order to change the speed of the bicycle
or to change its direction of movement.
Ask students to think about how forces work on a bike travelling along in a straight line. In small
groups develop a question they might explore to discover how different forces have different effects
on the movement of the bike
Help children
to decide what procedure they will follow and how they will measure the distance travelled by the bike
in each of the trials. Support groups to develop their recording sheets and to decide how they will
record their measurements. Collect results from several investigations and show children how to
record them and use them to draw a block graph using distances in whole numbers and categories
.
Once groups have conducted their experiment discuss as a class what they found out. Ask them what
makes a difference to how far the bike travels? Help them to realise that there are different factors
that make a difference
to how far a bike will travel forwards.
Discuss with the class how friction is a type of force that occurs between two surfaces touching each
other. Explain to students that depending on the surface it can be low-friction or high friction.
As a class make a list of everyday situations where high friction is helpful eg tyres on cars and
bicycles, goal keeper's gloves, tying shoe laces and everyday situations where low friction is useful eg
skating, playground slides.
Explain that the brakes on a bike work on the use of friction to slow down the rotation of the tyre.
Show pictures or demonstrate on a bike how the brake system of a bike works eg cables running to
the back and front small calipers pull on when the brakes are squeezed forcing the brake blocks to
press against the wheels. As they do so, friction between the blocks and the metal wheel rims make it
harder for the wheels to keep moving forward and bring you safely to a stop.
Conduct a braking experiment where students look at the use of brakes and friction. Ask students to
develop a question to be answered such as What happens when a surface is wet? How long does it
take to stop after braking? Does speed effect how long it takes to stop?
Ask students to predict what they think will happen in each of the experiments. Conduct the
experiment and have students measure different braking distances for controlled braking and
emergency braking situations as well as braking when the wheel rims are wet and dry. Record
measurements and discuss whether the experiments proved or disproved their predictions. Ask
students to share what they have learnt about how to brake safely on a bike and things they need to
consider when riding their bikes in order to stay safe.
As a class view the YouTube video about Gear systems - https://youtu.be/vX1-9C58-VM
Explain to the class that the push motion to turn the crank of the gear is the same as pushing down on
the pedal of a bike and making the front cog turn. Use a bike on a stand to demonstrate how rotating
the pedal causes the front gear to rotate and the bike chain then transfers that rotation to the back
gears.
View the Gears animation at https://www.exploratorium.edu/cycling/images/gears_animation.gif
Explain that this animation demonstrates the rotation of the front and rear cogs of a bicycle. Point out
to students how that for each turn of the larger front cog the rear cog turns twice. This is related to
the gear ratio on your bicycle.
Explain to students that to work out the gear ratio for a bike they count the number of teeth in front
chain ring and then the number of teeth in the rear chain cog. In this example the front chain ring has
54 teeth and the rear cog has 27. Explain that means every time you rotate the pedal once (our one
rotation of the front cog) the chain goes around 54 teeth. That means a 27-tooth (rear) cog goes
around twice (rotating the rear wheel twice). Explain that this means that the gear ratio is 2-to-1. Ask
students to record the number of teeth in the front and rear cogs of their own bikes and share them
with the class. The results could be recorded in a spreadsheet for comparison.
Discuss how some bikes will have more than one front ring and many rear rings. Ask students to
suggest why bikes might have multiple front and rear cogs.
Design an experiment that compares the bikes with a different number of cogs on the front and back
to find out which bikes can go faster, further with the least amount of force.
Record results and discuss findings of which bikes were more efficient and went further.
Students work in pairs to design their perfect bike based on everything they have learnt about forces,
braking and gears. For each aspect of their bike design they need to provide reasons for why it has
been included.
As a class, compare the different designs and predict which bike would be the safest, fastest and
most efficient giving reasons for their predictions.
Introduction to the Science of Cycling:
http://www.exploratorium.edu/cycling/introduction.html
Bicycle science: How bikes work and the physics behind them:
http://www.explainthatstuff.com/bicycles.html