Many students who do recognise that forces arise in pairs think that the two forces in a pair may differ in size

For instance, students may think that a larger object exerts a bigger force on a smaller object than vice versa.

Resources to Address This

• Describing interactions (14-16)

  Source - SPT/ Fm04TA04

  This resource provides a discussion framework for analysing interactions between objects.

  View Resource

• Forces exerted by distorted solids (5-11)

  Source - SPT/ Mf03PN02

  Compression and tension forces that create a balanced situation.

  View Resource

References

The following studies have documented this misconception:

• Gunstone, R. F. and White, R. T. (1981) Understanding of Gravity. Science Education, 65 (3),

  291-299.

  This study presented a sample of first year physics undergraduates at Monash University, Australia, with eight physical situations. The students were asked to make predictions as to what would happen if a certain action was taken. The action was then taken, and the subjects were asked to explain any discrepancies between their prediction and the result.
  Review sheet

• Brown, D. and Clement, J. (1992) "Classroom Teaching Experiments in Mechanics" in R. Duit, F. Goldberg, & H. Niedderer (Eds.), Research in physics learning - theoretical issues and empirical studies. San Diego State University, San Diego, CA.

  380-397.

  Review sheet