The study of circular motion at GCSE provides some conceptual challenges for students. Even though they do not usually have to engage with the mathematical treatment of this until A level, there are some potential counter intuitive ideas that arise which can cause problems at GCSE. The most common are listed below.
1) When objects move in a circular path they are accelerating even though 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 an indicator of acceleration is overlooked or played down.
2) When an object is moving in a circular path there is a force towards the centre of the circular path. Experiences on roundabouts, fairground rides and the widespread incorrect use of the term centrifugal force as an outwards one help to reinforce some alternative ideas.
3) If the force causing an object to move in a circular path is removed, it will travel off in a straight line as long as not other forces act upon it. The belief that an object will curve or spiral off, even when no forces are acting upon it is widespread.
The first of this is perhaps most challenging to address in class as it stems from a potentially incorrect definition or understanding of acceleration and so a revisiting of what acceleration is may be the best way to explore this. The first resources here, a video that could be reproduced in a class if you had a bowling ball and hammer, helps to try and address 2) and 3) above.
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