Many students think that a force is needed to keep an object moving with a constant speed

Forces and Motion

Misconception

Students may instead think that a constant speed results from a constant force – and the bigger the force on an object, the faster it moves.

Diagnostic Resources

• Measuring constant speeds (11-14)

This resource helps students to gain experience of timing objects moving at a constant speed and to recognise that the forces acting add to zero.

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• Constant (14-16)

How to use this word in the motion topic.

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• Episode 209: Drag air resistance terminal velocity (16-19)

Exploring the part played by gravity and drag when objects fall with constant velocity.

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References

• Watts, D. M. and Zylbersztajn, A. () A survey of some children's ideas about force Physics Education 16 (6) 360-365.

Many students in secondary schools have an unclear or incorrect understanding of the relationship between the motion of objects and the forces acting on them; this is particularly true when one of these forces is gravity. The researchers identify a range of student misconceptions and suggest that teachers need to use these as starting points to develop activities which challenge students to overcome them.

Paper digest

• Tao, P. K. and Gunstone, R. F. () The Process of Conceptual Change in Force and Motion during Computer-Supported Physics Instruction, Journal of Research in Science Teaching: The Official Journal of the National Association for Research in Science Teaching, 36 (7) 859-882.

It is common for students to confuse the concepts of force and motion, leading the ideas such as a constant resultant force will cause movement at a constant speed or that a motionless object cannot have a force acting on it. This research shows that analysing a wide range of scenarios is required to effectively reduce student misconceptions and that care must be taken when moving between contexts otherwise students may quickly revert to their prior beliefs.

Paper digest

• Halloun, I. A. and Hestenes, D. () Common sense concepts about motion American Journal of Physics 53 (11) 1056-1065.

Many students incorrectly believe that moving objects must be experiencing a driving force and that a constant force will cause uniform motion rather than acceleration. This research shows that these ideas need to be challenged repeatedly, using a wide range of examples and demonstrations for students to start to move towards scientific descriptions.

Paper digest

• Trumper, R. and Gorsky, P. () A cross-college age study about physics students' conceptions of force in pre-service training for high school teachers Physics Education 31 (4) 227-236.
• Twigger, D.; Byard, M.; Driver, R.; Draper, S.; Hartley, R.; Hennessy, S.; Mohamed, R.; O'Mally, C.; O'Shea, T. and Scanlon, E. () The conception of force and motion of students aged between 10 and 15 years: an interview study designed to guide instruction International Journal of Science Education 16 (2) 215-229.

Students can be very unclear about the difference between energy and force, often believing that they are the same thing. This leads then to the idea that objects slow down because they are ‘using up’ energy, rather than realising that forces are acting to change the motion. This study suggests that careful analysis of motion graphs, coupled with force diagrams can help overcome these issues and that the concept of momentum should be introduced earlier in many courses.

Paper digest

• Klaassen, K.; Westra, A.; Emmett, K.; Ejkelhof, H. and Lijnse, P. () Introducing mechanics by tapping core causal knowledge Physics Education 43 (4) 433-439.

The motion of comets can be difficult for students to understand with many unable to describe the effect of gravitational forces correctly. This research identifies a range of misconceptions which need to be overcome before students can give scientific explanations, emphasising that students need to understand the Newtonian concepts of force, clearly linking force to acceleration, and become able to ‘visualise force’ before they attempt to explain how and why comments orbit the Sun.

Paper digest

• Hewson, P. W. () Epistemological commitments in the learning of science: Examples from dynamics The European Journal of Science Education 7 (2) 163-172.

This study took place at the University of the Witwatersrand, South Africa. It aimed to explore the role played by the epistemological commitments which a student holds in determining whether he or she accepts or rejects an argument.

• Lythott, J. () "Aristotelian" was given as the answer, but what was the question? In H. Helm and J. D. Novak (Eds.), Proceedings of the International Seminar: Misonceptions in Science and Mathematics Cornell University Ithaca, NY, 257-265

The self-proclaimed purpose of this paper is "to raise questions concerning the advisability of the continued use of such adjectives, specifically "Aristotelian", without a concerted effort to understand whether or not it is an appropriate label for what it purports to describe."

• Watts, D. M. () A study of schoolchildren's alternative frameworks of the concept of force International Journal of Science Education 5 (2) 217-230.

This study used an interview approach to identify the conceptions of force of 12 students aged 11-17. Students were drawn from a range of schools in the Greater London area, from both junior science classes and advanced-level physics classes.

• Clement, J. () Students' preconceptions in introductory mechanics American Journal of Physics 50, (1) 66-71.

• Ogborn, J. () Understanding students' understandings: An example from dynamics International Journal of Science Education 7 (2) 141-150.

• Saltiel, E. and Malgrange, J. L. () 'Spontaneous' ways of reasoning in elementary kinematics European Journal of Physics 1 (2) 73-80.