Introducing and rehearsing vocabulary that allows students to describe observations accurately is an essential first step towards understanding motion. Students do not usually make a clear distinction between speed and acceleration. Often students do not use the word acceleration outside of their science lessons, and instead talk about speeding up or slowing down. Acceleration may be seen as ‘going fast’ (Driver et al., 1994).

These questions are designed to investigate students’ understanding of acceleration when objects are either speeding up or slowing down.

Students should complete the questions individually. This could be a pencil and paper exercise, or you could use an electronic ‘voting system’ or mini white boards and the PowerPoint presentation. The follow on question will give you insights into how they are thinking and highlight specific misunderstandings that some may hold.

Differentiation

You may choose to read the questions to the class, so that everyone can focus on the science. In some situations it may be more appropriate for a teaching assistant to read for one or two students.

1a. A 1b. B 2a. A 2b. C

Q1. The car has the most acceleration because it reaches 60 mph in a shorter time. Some students may confuse acceleration for how fast the vehicles are going and choose answers C, A. If students choose the lorry, they are probably thinking of acceleration as a pushing force, which is confirmed with answer C for part b. Answer D for part b indicates students who are choosing an answer based on past experience rather than working it out from the evidence provided.

Q2. The car has the biggest acceleration because it slows down more in the same amount of time. Answer D for part b is correct, but is only a partial explanation. Answers B, B suggest students are thinking of the force needed to slow the lorry. Answers C, A shows that students are considering the end point only. It is quite common for students to ignore the time involved in speeding up and slowing down.

The correct reasons given in these answers define acceleration in two different and complementary ways.

If students have misunderstandings about identifying acceleration in different situations, it can help to discuss with the class what happens to a car when it accelerates.  It is easy to find video clips of cars accelerating that describe acceleration in terms of the time it takes to speed up from 0-60 mph, say. Discussing what this means in pairs or small groups could encourage social construction of new ideas through dialogue. Giving students the opportunity to write a definition of acceleration in their own words can consolidate learning and check individual understanding. This can be extended to explain why slowing down is also acceleration.

The following BEST ‘response activity’ could be used in follow-up to this diagnostic question:

• Response activity: Is it accelerating?

Driver, R., et al. (1994). Making Sense of Secondary Science: Support Materials for Teachers, London: Routledge.