Newton's Second Law
Forces and Motion

Trolley forces

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Motion of a trolley.

The purpose of this activity is to involve pupils in discussion about resultant forces. How will various forces affect the motion of the trolley?

What to Prepare

  • dynamics trolley
  • two pulleys
  • two sets of 100 gram masses and hangers

What Happens During this Activity

With the trolley set up as in the diagram, pupils can predict and observe the effect of different combinations of forces acting on the trolley. There are two important strands to the discussion. In which direction will the trolley move? What type of motion (speeding up? slowing down? constant speed?) will result from forces which do not add to zero?

Whilst you have a situation where all forces add to zero, it is a good idea to invite someone to cut the string on one side of the trolley. The resulting discussion will allow you to assess how far the learners have appreciated the ideas (the trolley gets going in one direction due to the action of the resultant force).

You might like to use this model to support the discussion about their predictions:

Newton's Second Law
is expressed by the relation F=ma
can be used to derive Kepler's First Law
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