Force
Forces and Motion

Canal boats

Classroom Activity for 14-16 Supporting Physics Teaching

What the Activity is for

This is a rather open-ended investigation, where students can use their evolving understanding of force and motion both to shape their expectations of the effects of their interventions in setting up the experiments and in interpreting the outcome.

The essential ingredient is an anti-linear airtrack, where there are many and varied forces at work on the moving object. How you motivate engagement with this is up to you. There is a suggestion below.

It is a rich environment, so you'll need to structure the challenges you set to match your students.

What to Prepare

  • a prepared length of semi-circular guttering, sealed at both ends
  • a blow-moulded boat, approximately 4 centimetre beam and 12 centimetre waterline length.
  • a pulley
  • 10 gram hanger masses
  • some thread
  • some 5 gram masses to load boat
  • a metre ruler
  • a stopwatch
  • a plastic litre jug to fill and empty the waterway

What Happens During this Activity

Students are invited to offer advice to a rapid-transit-freight investor to maximise the profits – assumed to be achieved by carrying as much as possible down a waterway as rapidly as possible.

Introduce the options. The owner can:

  • Buy a more expensive engine and so increase the driving force, reducing the trip time.
  • Pay higher fees so that the waterway owner keeps more water in the waterway, thus reducing the retarding force.
  • Carry more load each time.

This sets up a nicely open-ended investigation, where there are many interacting variables, and careful measurement will be needed to offer useful advice. You will probably need to match the laboratory model to the real situation, including making clear how the objects in the lab model the real objects.

With some encouragement, the output from the experimental phase is likely to be one or more graphs with appropriately controlled variables. These will be data for the next phase, which will try to relate these results to the original challenge. It's unlikely that any one group of students will achieve a comprehensive set of results, so this can also be a useful exercise in appreciating the limits of evidence.

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