The study of circular motion at GCSE provides some conceptual challenges for students; the most common alternative conceptions are listed below, it is hoped that the resources below will help support their learning.
- When objects move in a circular path they are ‘not’ accelerating because they are travelling at constant speed. Students often think this because they have learnt or assume that acceleration only means speeding up or slowing down and the fact that a change in direction is also acceleration is overlooked.
- When an object is moving in a circular path there is a force ‘away from’ the centre of the circular path. Experiences on roundabouts, fairground rides and the widespread use of the term centrifugal force help to reinforce this way of looking at things, but this is in contradiction to the fact that a force towards the centre is what is required to keep going around in a circle.
- If the force causing an object to move in a circular path is completely removed, the object will leave along a ‘radius or spiral off’ the circular path. Whereas in fact it will move off the circular path along a tangent.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
Links and Resources
This resource from the institute of physics was written to introduce AS physics students to circular motion so it sits nicely in the GCSE triple science framework, extending the previous work on forces. It describes a lovely series of demonstrations – you really must try for yourself the one with the jelly - which should get your students thinking and developing their own ideas.
Although most will already know about whirling a bucket of water around without the water falling out, it still has to be done! The table at the bottom of page 2 would make a useful cut and stick activity where students have to match the force to the example. Teachers will appreciate the practical tips and the background notes on the physics involved.
This film is really short but it’s super! It would make an excellent introduction to circular motion as there is effectively no gravity. Challenge your students to explain the motion of the car and then ask them again at the end of the topic to assess the progress they’ve made. Of course the centripetal force comes from the track rather than the car as suggested by the notes. The other half of the force pair is the force from the car on the track.
This article, written for GCSE level students, provides a good example of circular motion in action for “reading around the subject” and as such it would be useful to read as part of a piece of homework. Consider asking students to explain the article to an adult family member when they have read it. The adult then signs the homework diary to confirm that they have discussed the article with the student. The discussion will be worthwhile for all concerned and doesn’t require any marking.
The two cartoon characters in this short video clearly and convincingly explain Newton’s reasoning behind the circular motion of the Moon. Show it to your students if they are unsure about how satellites like the Moon orbit the earth.
It may have been complied in the sixties but this collection of practical ideas is highly recommended as a resource for you to use. It is included here for the suggestions on circular motion. For idea 5 use a rubber ball rather than stone and you have a great demonstration that you can use to discuss the variation in the tension as the ball loops the loop.