US-based researchers investigated 19-year-olds ability to apply the concept of acceleration when interpreting the motions of real objects.

Evidence-based suggestions

• Emphasize concept formation and scientific reasoning through lab work, discussions, and exams, encouraging students to apply concepts to real-world motion.
• Findings reveal standard course students struggled to grasp acceleration in the time usually allotted, suggesting dedicating more time to basic kinematic concepts at the introductory level, even if it means omitting advanced topics.

Learners’ ideas

Students were unable to differentiate between the concept of velocity and a change of velocity.

• Students often used the word over in defining acceleration but did not always refer to the relationship between the numerator and the denominator of the equation for acceleration. For the students over was equivalent to during.
• Students realised that acceleration includes a change in velocity but did not always recognise that it also includes a time interval during which this change occurs.
• Some students believe that catching up to something means having a greater acceleration.
• Some students believe that when two balls reach the same position they have the same acceleration.
• Sometimes students would state that the ball that was ahead would have a greater acceleration.
• Students attempted to compare accelerations on the basis of final speeds alone.
• Some students assume that covering a greater distance at the same time must mean an object has a greater acceleration.
• Some students may not be able to compare instantaneous velocities at different times.
• Some students expressed the belief that when the direction of the ball changed, the direction of the acceleration changed and therefore had to pass through zero.

The study

Aims

To investigate "the ability of students to apply the concept of acceleration in interpreting simple motions of real objects".

How the evidence was collected

The tasks given to students were replicated and developed from the work of Jean Piaget. Student interviews were then conducted according to a standard questioning format but the interviewer could choose to probe more deeply into a student's understanding by extending the discussion. During interviews, students were asked to perform 4 motion tasks (3 involving uniform speed, and 1 dealing with uniform acceleration). The interviews lasted 20-30 minutes, were audiotaped and occasionally videotaped. Often questioning about acceleration was preceded by the administration of speed comparison task.