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Misconceptions in mechanics and how to avoid them

Many studies have been  carried out recently in which ideas about mechanics, held by people from a wide range of age and sophistication, have been explored (see Osborne et al (1983) for a comprehensive list of references). These studies have uncovered inconsistencies and contradictions in the application of concepts to simple real-life situations. Interpretations of the results usually centre round the notion of ‘alternative frameworks’, that is, ways of viewing the world which differ from those held by ‘scientists’. These  are often reminiscent of pre-Galilean ideas. I have argued (McClelland 1984) that such interpretations include an implicit assumption that the subjects  should have had history of experience and instruction adequate  to lead to formation of concepts  coherent with a scientific view. In general I do not believe this to be the case, so that  an alternative xplanation in terms of inadequately clarified and differentiated concepts remains plausible. At school level mechanics consists of a rather small number of superficially straightforward ideas and rules which apply very accurately to bodies and processes as commonly e‘xperienced. Admittedly some non-trivial assumptions about the nature of time  and space must be made,  and  it must be accepted that, at high relative speeds and at very small scale, the rules may cease to apply, but it might be supposed that what remains would be easy to learn and that most pupils would master it. All that should be needed would be to (i) define terms and  concepts  unambiguously, (ii) use them consistently with wide exemplification and (iii) explain their limits of applicability. Unfortunately, as teachers, we persistently fail on all three counts.