Forces and Motion

Speed limits

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Talking about speed.

The purpose of this activity is to focus pupils' attention on the idea of speed, where it occurs in everyday life and what units it is measured in. You may also to start clearing up some difficulties:

  • How average speed differs from instantaneous speed.
  • The differences between the time shown on a clock and the time intervals used to calculate speeds.

What to Prepare

  • pictures of speed limit signs, speed cameras or a police speed trap
  • stories of journeys, told in pictures, video clips, or words

What Happens During this Activity

Pupils use the visual stimuli to talk, in groups, about speed. Pupils will probably talk about speed in miles per hour (mph). This is fine for a starter activity. The police use a variety of methods to check the speed of moving vehicles. One technique is to time a vehicle as it moves between marks on the road. Painted white squares on roads provide police officers with markers. Bridges are also used as start and stop markers.

You could use it, with advantage, to explore the difference between time of day (o'clock) and time interval, or duration.

Teacher: When was she doing 40 mph?

Teacher: For how long was she getting farther away from the town?

It's also a natural place to start distinguishing between average and instantaneous speed, asking questions such as:

Teacher: How far did she go in that hour? What was her top speed?

Teacher: For how long did she keep it up?

appears in the relation SUVAT Equations
can be represented by Motion Graphs
has the special case Wave Speed
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