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

Forces and Motion


For instance, pupils 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


The following studies have documented this misconception:

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


    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.

  • Brown, D. and Clement, J. () "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.



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