Many pupils do not clearly distinguish the ideas of instantaneous and average speed.

Forces and Motion

Misconception RESEARCH REVIEW

Resources to Address This

  • Speed limits (11 - 14)

    Source - SPT/ Mo01TA01

    This resource supports classroom discussions on how average speed differs from instantaneous speed.

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  • Average speed and instantaneous speed (11 - 14)

    Source - SPT/ Mo01PN05

    It is common to use the term speed rather than average speed. Many teachers drop the term average thinking it may add an additional level of difficulty. We would nevertheless recommend that you encourage your pupils to make the distinction between instantaneous speeds and average speeds wherever possible. One way to do this is to restrict the use of average speed to refer to a whole journey. 

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  • Instantaneous and average velocities (11 -16)

    Source - Practical Physics/ Force and Motion/ Time, distance and speed/ ...

    You can use a sensor data logging system to experience the difference between instantaneous and average velocity.

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  • Episode 205: describing motion (16 - 18)

    Source - TAP/ Mechanics/ Kinematics

    This is an area which many moderate-to-weak students find difficult and they may well remember their pre-16 experience with some unease. It is worthwhile including a direct measurement activity to ensure that students spend sufficient time on the basic physics of velocity, distance and time.

    View Resource

References

The following studies have documented this misconception:

  • 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.

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