## Many students think that an object moving in a circle experiences a force away from the centre of the circle (a centrifugal force)

Forces and Motion

Misconception

### Diagnostic Resources

• Whirling a rubber bung on a string (11-16)

Source - Practical physics/ Force and motion/ Circular motion

This resource in an introduction to exploring circular motion with your students.

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• Circular motion (11-14)

Source - SPT/ Es02PN02

To make anything move along a circular path it is essential to have a force that acts towards the centre of that path.

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• Episode 224: Describing circular motion (16-19)

Source - TAP/Mechanics/ Circular motion

Motion in a circle is an everyday occurrence and the students should be given time to discuss their experiences of such motion. It is important that they should actually feel the force exerted when an object on a string is whirled round their head.

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## References

The following studies have documented this misconception:

• McCloskey, M., Caramazza, A. and Green, B. () Curvilinear Motion in the Absence of External Forces: Naïve Beliefs About the Motion of Objects. Science, 210 (4474),

1139-1141.

University students were asked to draw the path a moving object would follow in several different situations. Over half of the students, including many who had taken physics courses, evidenced striking misconceptions about the motion of objects. In particular, many students believed that even in the absence of external forces, objects would move in curved paths. The sample comprised 47 students, 15 of which had no formal physics education, 22 of which had high school physics, and 10 of which had college-level physics.
Review sheet

• Klaassen, K., Westra, A., Emmett, K., Eijkelhof, H. and Lijnse, P. () Introducing Mechanics by Tapping Core Causal Knowledge. Physics Education, 43 (4),

433.