Circular motion.
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.
Circular Motion and Bowling Balls
A YouTube video demonstrating a bowling ball moving in a straight line then a centripetal force is applied using a hammer resulting in circular motion. A very clear demonstration in a real world situation that allows students to understand where forces are applied to provide circular motion.
Episode 224: Describing Circular Motion
From the Institute of Physics, this learning episode introduces students to the importance of circular motion and the need for a centripetal force to keep an object moving along a circular path. The activities include: observing circular motion, whirling bucket and centripetal force, discussing examples of centripetal forces, further demonstrations of centripetal force.
Astro Academy: Principia
This website provides resources including orbital experiments conducted by astronaut Tim Peake aboard the International Space Station; dynamic analyses of the results; ground-based analogue experiment guides for students and teachers; and a suite of further space science and education guides.
Playing with Toys in Space *suitable for home teaching*
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.
Flying Weightless *suitable for home teaching*
This Catalyst article looks at what it means to say that an astronaut is 'weightless'. The article looks at how astronauts are trained in aircraft and how underwater work can help prepare them for space travel.
Why Doesn't the Moon Fall Down?
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.
Ladybird in Circular Motion
A Phet simulation that demonstrates position, velocity and acceleration vectors. Move the ladybird by setting the position, velocity or acceleration and see how the vectors change. Choose linear, circular or elliptical motion, and record and playback the motion to analyse the behavior.
Nuffield Physics: Questions Book V
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 five 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.
