May the Forces be with You – Lesson 1 – Sporty Forces
Students develop their understanding of forces by thinking about pushing a car and being in a tug-of-war activity in small groups. These are used to introduce arrows to represent forces. Then students throw and catch different mass balls. Throughout we introduce the language of forces and concepts of mass, distance, time, speed, momentum, acceleration, inertia, and friction.
Introduction: Forces and Arrows One of the most important ideas in the modern world is forces because they make things move. Another important idea is using arrows to represent things. We use arrows in this lesson to represent the strength and direction of student-created forces.
Forces and motion: Because forces make things move, this lesson introduces the language of motion: force, distance, mass, speed, acceleration, deceleration, and momentum (combination of speed and mass). We use a Word Wall for these words.
Pushing a car: Teacher-led discussion/optional activity The lesson begins by asking students to visualise pushing a car in the teacher’s car park (we encourage pushing a car if this is permitted). We use this to introduce the language of motion, and we use arrows to represent students' individual forces and then to combine them all together. Magnetic arrows, one for each student, lets them add their arrows head to tail on the whiteboard and understand the combined arrow as a large force.
Tug-of-war Activity: Small group (5 or 4 students) activity about adding and cancelling forces in a tug-of-war tournament. Students pull against each other in one-on-one tugs, represent the near-cancelling forces with arrows and determine their rank order (see worksheet). Finally they do a 2-on-3 competition to see if the three weakest can beat the two strongest.
Sports activity: throwing, catching and feeling the momentum of heavy and light balls: Small groups work with ping-pong balls and basketballs to reinforce the concepts introduced above by doing simple throwing and catching activities plus a “feeling momentum” activity.
Extension activities in sport: Reinforce student learning by using the newly learned vocabulary in other sport activities.
Review and introduce the next lesson: Identify and review all new words and start the class Word Wall.
Students will:
- explain the meaning of mass, distance, time, speed, momentum, inertia, acceleration, force and friction
- show how arrows can be used to visualise forces and how they can add and cancel
- explain the role of mass and forces for making things go faster (accelerate) especially in sporting activities such as throwing and catching different mass balls.
- Review the Year 4 May the Forces be with You Lesson 1-4 and 5-8 PowerPoints.
- PrimaryConnections has useful teaching resources for teachers not familiar with word walls and science journals:
- This lesson relates to physical education activities. Every aspect of physical education activities involves application of forces using our muscles. It will be very beneficial if the concepts presented here are incorporated into physical education discussions, especially the language of arrows (see word wall below) and the idea of using arrows to represent forces.
- The website https://kiddo.edu.au/ is an excellent Australian resource for teachers of science who are not able to work with a physical education specialist and may not be familiar with approaches to teaching the fundamental movement skills.
- Students learn the language and ideas of mass, distance, time, speed, momentum, inertia, acceleration, force, friction in the context of their physical skills development lessons in physical education. Students participate in each of the activities and use the ideas and words above to describe the effect of forces in each game.
- Read our ‘Using models and analogies in teaching science’ guide.
- Some physical education equipment will be needed. See equipment list below.
- Ropes for 2–5-person tug-of-war activities – for example skipping ropes.
- Low mass balls and high mass balls. For example, ping pong balls and basketballs and a selection of other low-cost balls of varying mass, including tennis balls (but no golf balls or heavy cricket balls).
- Optional: If the activity is considered appropriate, then a car (with an adult driver for steering and braking) for students to push about 10 metres in the school car park or on a level netball or basketball court.
Start the lesson in the classroom by using the May the Forces be with You PowerPoint to provide an overview of the eight lessons and of the module and outline the Lesson 1 learning intentions.
Explain the importance of using words accurately to describe the effect forces have on objects.
Put up key words on the Word Wall. Use the explanation chart if needed.
- Distance – what is distance? How do you measure it?
- Time – what is time? What units do we use to measure time?
- Speed – who can explain speed? What units are used to measure speed?
- Acceleration – what is acceleration?
- Mass – how many kilograms are you? How many kilograms is a car? (1500 kg is typical)
- Inertia – which would have most inertia: you, the car or the big truck?
- Momentum – Depends on speed and mass. Momentum is bulletiness, it causes damage.
- Arrows – show two things about forces: the strength of the force by its length, and its direction.
After adding key words to the word wall, move onto the next activity.
We will start the lesson with an ‘imagine’ experiment. Who has pushed a car?
This is a ‘pretend’ activity but could be a real activity if a suitable car was available in a safe car park. The idea is to imagine the class is pushing a car in a flat car park. Predict what will happen.
Use creative questioning and encourage all students to contribute answers to what will happen and why will it happen. Follow these steps of activities and questioning with the students.
- Brakes on, all class pushing. What happens if the handbrake is on, so the wheels won’t move? (The car won’t move.)
- Why won’t the car move? – The car won’t move because the brake pads make friction to stop the wheels turning, and the tires have friction on the road. If you pushed hard enough the tires might slide on the road. Has anyone seen black lines on roads where tires have made skid marks?
- Brakes off, one student pushes. Teacher is sitting in the driver’s seat. What happens? Car slowly starts to move and gradually gets faster. (The friction, which is a ‘stopping force’, is removed and the car will start to move. However, its speed will be very slow.)
- More students pushing. Now what happens? Car speeds up faster: this is called acceleration. Why does it speed up faster? (more students, more force).
- Whole class pushes. More force, more acceleration, car speeds up even more. Why? (The car moves faster again because the force pushing the car is much bigger than when there was just one person pushing). Soon everyone has to run to keep up with the car….then they can’t push properly.
- (Imagined) Collision. Imagine pushing the car right across the car park where there was another car parked! What happens when they hit? You have made the car go fast. It has momentum…a combination of speed and mass. It does not want to stop because it has lots of inertia. What sort of damage might it do? Why? (Because it takes lots of force to make a car stop quickly, and that force is enough to dent both of the cars!).
- Pushing a big brick truck What if it wasn’t a car but a fully loaded brick truck? (It would speed up much slower.)
Pushing and the maths of arrows. Each student’s force is shown as one magnetic arrow on the white board. Let’s do an arrow for the whole class pushing: every child should add their arrow on the white board. (Arrows must be put head to tail) until there is a huge arrow.
Teacher Introduction
Tug of War is about forces and friction. You pull with your muscles. Friction stops you from sliding on the ground and stops the rope from sliding through your hands. The friction force must be more than the pulling force or else you will slip and slide.
Arrows demonstration
Ask two students to demonstrate a two-person tug-of-war in front of the white board. Each person’s pulling force is represented by an arrow drawn on the white board.
Draw arrows to represent the forces each student applies. First pulling gently, then stronger. The arrows show the pull direction. They are equal until one person starts to move. Then the winner’s arrow must be longest, the loser’s is shorter. If a person easily wins, their arrow is much longer. If it’s a close match, then the arrows are nearly equal.
Friction discussion: What is friction? It is the force that stops things from sliding. Friction between hand and rope, friction between feet and the ground.
Size and strength: Does being bigger help? Bigger and heavier always helps in a tug-of-war. It doesn’t matter if your arrow is the biggest or the smallest.
Class tug-of-war
Conduct a whole class tug-of-war. This activity could be done during physical activity time, tall team vs short team, gloves on vs gloves off, shoes on vs shoes off, etc..
In preparation for the third part of this lesson the teacher leads a discussion based on the following questions. (Write key concepts on the white board)
- What is the difference between throwing a ping pong ball and a basketball? (Basketball is heavy, needs more force to speed it up)
- What determines how high you can throw each ball? (For the ping-pong ball, height depends on the speed you can move your hand, for a basketball depends on the force you can exert.)
- What if you were to throw a balloon: why won’t it go far? (The wind or air resistance.)
- What sized ball do you think you could throw the highest? (The basketball limited by its weight, ping-pong ball by wind resistance…something in between like a tennis ball may be the best)
- Suppose you had a very heavy glove on your hand. Could you throw as high as before? Why not? (Now you have to speed up the glove as well as your hand, that is like speeding up the rolling car…you have just added mass, your hand may not get up to speed.)
- What could you do to make the balls go higher? (Use a bat or a racket because the end of a long thing can go much faster than your hand and you can transfer energy from the bat to the ball.)
- Why do cricket and baseball batters wear helmets with face shields? (If they missed the ball it could severely damage their face and head.)
Throwing Activity
Choose a location where there is a building or a tree to use to judge the height that the balls go (e.g., top of roof, second floor veranda, second branch on the tree)
Students take turns in being throwers, catchers and observer/recorders. Each student takes turns throwing a ping-pong ball and a basketball vertically upwards. The catchers try to catch them.
Use results to predict what type of ball you could throw highest. Then ask your teacher if you can select some balls to test the prediction.
Have the students complete this group worksheet. Complete a table with a list of people, type of ball and rough height estimate.
Catching activity
Watch the brief video of a person catching a fast cricket ball. See how the catcher moves their arms to absorb the impact.
In small groups form a circle for throwing and catching. How do you change your actions according to the mass and speed of the ball?
Observe carefully how you need to catch a basketball compared with a ping pong ball. For the basketball you have to remember it has much more momentum due to its mass and you need to move your hands in the direction of the ball until it stops. The same is true when you catch a cricket or baseball that is moving very fast. Discuss observations in the group, repeat activity so everyone can see. Record results on worksheet.
Impact Activity
In pairs, take turns in throwing balls gently at each other’s back. Feel the impact. Guess what sort of ball it was. Describe what it feels like for fast and slow balls of different types.
Review and introduce the next lesson
Review the new words for the May the Forces be with You Word Wall. Explain that in Lesson 2 we will make a force measurer and learn about how we measure forces.
Optional Extension: Continually reinforce concepts
Everything we do involves forces. When students learn or practice new skills, ask them to think about the forces they have to apply, where these forces come from and the effect they have. Questions could include:
- What forces are involved in this skill?
- Which muscles are you using to make the forces?
- How do you move your body to help make the forces larger?
- What arrows can you use to show the forces?
These questions could be applied to almost any physical activity: running; hopping; skipping; kicking; balancing; dodging; soccer or basketball dribbling.
The Kiddo website at https://kiddo.edu.au/skills is an excellent resource to support students, classroom teacher, physical education specialist, parents and community coaches with details of how to perform the skills listed.
Optional Extension: Tug-of-war tournament
Students need to be in groups of five (4 is OK), each group has a rope, and a clipboard with worksheet for recording arrows for their forces. If they are balanced the two arrows are equal. If one side wins then the winner’s arrow is longer than the other. Students test each other in pairs.
The following points will be helpful in conducting the activity:
- Note: Only the relative arrow length is important because we are not measuring, just comparing. Draw two arrows, one for each direction. If balanced the arrows are equal, if one person wins their arrow is longer.
- The challenge is to make a list of force arrows from the strongest to the weakest.
- Finish with combined teams such as a three-person team against a two-person team. (two strongest against 3 weakest). Can the three-person team beat the two-person team?
- Students draw in the combined arrows. Are the three shortest arrows greater or less than the two longest arrows?
- The following two pages have a recording worksheet and sample of completed worksheet.
The recording sheet may be useful in helping students record results. A completed example can be found here.
Force: A Push or a Pull.
Distance: How far apart two or more objects are.
Mass/Inertia: A measure of how much force is needed to change an object’s speed – to make it move, stop, speed up or slow down.
Time: Describes when an event occurs, normally described as being in the past, present, or future.
Speed: is a measure of how far an object travels in a certain amount of time. Speed in science is normally measured in metres per second, while kilometres per hour (km/h) are used in everyday applications, such as measuring the speed of a car.
Acceleration: is a measure of a change in speed. We feel a change in speed when something gets faster and faster or slower and slower.
Momentum: is the combined effect of the mass and the speed of an object. A heavy and fast object, like a basketball, has large momentum. This is why it can hurt to catch a fast-moving heavy ball. Your hands need to absorb that momentum. We often refer to momentum as ‘bulletiness’ because it has the ability to cause damage.
Friction: is a force that is in the opposite direction to an object’s movement and causes the object to slow down. We feel friction whenever we slide something.
Fun Fact! Friction doesn’t always cause objects to slow down, you actually need friction to start walking. Friction stops your foot from sliding, allowing you to walk forwards. A car needs friction to start driving. Friction stops the car’s wheel from sliding on the road. Friction provides traction!