3. Organising investigations into friction
Resource 4: Summary of forces summarises what a teacher could be expected to understand on forces and motion.
Primary pupils need to experience a range of practical experiences and have chances to talk and think about what they have been finding out. There are many activities that would extend your pupils’ ideas about forces, for example looking at balls rolling down slopes at different angles and pushing or pulling shoes along different types of surface.
Case Study 3 shows how Mr Peter reflects on what he has achieved with his class. How do you reflect on your learning and that of your pupils? What would you record about your learning in this topic?
In the Key Activity, you guide the pupils through thoughtful investigations around a force that slows objects down – friction. This extends the work of Activities 1 and 2, where you encouraged pupils to speak their ideas. At the same time, you can assess their developing understanding by listening carefully to what they say.
Case Study 3: Reflections of a teacher
Here are Mr Peter’s notes on what he feels his pupils have gained from doing half a term’s work on force. (This involved a number of different experiments and discussions, those in this section and some based on the ideas in Resource 6.)
- Confident they know forces are pushes or pulls or combinations of both
- All pupils know that forces are involved when things start and stop moving and make turns.
- Some pupils know that the forces on a stationary object are equal and opposite but many find this difficult, as they can’t see any forces acting.
- They have good experience of most forces that require actual contact – but many are not sure about forces exerted over a distance (for example repulsion and attraction of magnets and static electricity).
- The class is pretty clear about effects of gravity and most pupils have some idea that ‘weight’ is the force they exert on our planet and that this would change if they were on a different planet.
- Need more work on friction. Some pupils still puzzled that friction can be both useful and a problem.
Need to improve our models of force meters, which show how to measure forces accurately.
Key Activity: Reducing friction
Give your pupils opportunities to work in groups (see Key Resource: Using group work in your classroom) to set up their own investigations.
This investigation looks at reducing friction. Write this question on the board: Which substances are better at reducing friction? Some ideas of substances to use are chalk, cooking oil, margarine and soap, but let your pupils try their own ideas. (See Key Resource: Using investigations in the classroom.)
Depending on the equipment you have:
Pupils could use a shoe with weights (heavy stones would be ideal) on a piece of wood. If they tilt the wood the shoe will slide. The more they need to tilt the wood the greater the friction. How does the angle change when they rub different substances on the wood?
Or pupils could use an elastic band to propel a coin across different surfaces. If the elastic band is pulled back the same amount each time, the coin will get the same pushing force each time. Pupils can then measure how far the coin travels on different surfaces.
Support their planning of investigations including their predictions – what they think will happen and why. How will they clean the wood in between experiments? How many times will they try each substance? Resource 5: Investigating frictionprovides a planning sheet to help pupils with their investigations.
Give them plenty of time to carry out the experiment. Encourage them to record their results in a table.
At the end of the investigation, ask them to explain what their results mean. What advice would they give to people who wanted to know how friction could be reduced? They will be behaving, talking and thinking scientifically – which is great.
Think about how your pupils could present their work: will you ask each group to present to the class? Or make a poster to show their results?
(Look at Resource 6: More ideas for experiments around forces for how to support and encourage more investigations.)