# Many pupils have an unclear idea of acceleration and cannot reliably separate it from speed

Forces and Motion

Misconception

Pupils can sometimes struggle to distinguish the notion of acceleration from that of speed (or velocity). Pupils may think, for instance, that if an object is said to have a large acceleration, it must have a large speed.

### Diagnostic Resources

The following worksheets may help to identify whether students hold this particular misconception.

• Starting with Acceleration

This resource provides a good starting point for pupils who may be encountering acceleration formally for the first time. It lays a solid foundation which can be built upon later in their education.

One 'trick' is to refer the acceleration values as 'change in metres per second ... every second' repeatedly, before moving to using 'metres per second squared'.

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• Velocity-Time Graph and Acceleration (14-16)

This resource suggests that one way to get a handle on velocity is to start with acceleration.

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• Increasing and Constant Speeds (5-11)

This resource focuses on a falling dandelion seed, noticing its changing speed.

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• Distinguishing between velocity and acceleration (11-16)

This experiment isolates the effect of a constant force on a trolley: it changes velocity while keeping acceleration constant. Data logging eliminates calculations and shows instant acceleration.

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• Episode 211: Newton's second law of motion

Activities to emphasise the quantities involved in Newton's second law - force, mass, acceleration - and illustrate the difference between velocity and acceleration.

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## References

• Maloney, D. P. () Rule-governed physics: Some novice predictions. European Journal of Science Education, 7 (3), 295-306.

Students can struggle with the concepts of acceleration, velocity and weight. First-year US college students took comparative pencil-and-paper tests to identify the strategies they employ when predicting the behaviour of typical systems involving these topics.

Paper digest

• Jones, A. T. () Investigation of students' understanding of speed, velocity and acceleration. Research in Science Education, 13 (1), 95-104.

From this study, it is clear that students can conflate velocity, speed and acceleration. With a sample of 30 students aged 11-16 in the US, the researchers found that confusion around one object passing another appeared regularly.

Paper digest

• Trowbridge, D. E. and McDermott, L. C. () Investigation of student understanding of the concept of acceleration in one dimension. American Journal of Physics, 49 (3), 242-253.

US-based researchers investigated 19-year-olds ability to apply the concept of acceleration when interpreting the motions of real objects. They found that students struggled to grasp acceleration in the time usually allotted, suggesting the need to dedicate more time to basic kinematic concepts at the introductory level, even at the cost of advanced topics.

Paper digest

• Clement, J. () Students' alternative conceptions in mechanics: a coherent system of preconceptions? Helm, H. and Novak, J. D. (eds), Proceedings of the International Seminar: Misconceptions in Science and Mathematics. Cornell University, Ithaca, N.Y., 310-315.

This study highlighted common ideas among students, including the ideas that a force can be used up; a force inside a moving object is what keeps it going and if there is motion, there must be a force in the direction of motion. They suggest teachers develop metaphors which organise intuitions the student already has.

Paper digest

• 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.

• Driver, R.; Squires, A.; Rushworth, P.; Wood-Robinson, V. () Making Sense of Secondary Science. Routledge, London.