Forces and Motion | Properties of Matter

Sinking a punt

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Loading a boat until it sinks.

In this activity pupils measure how the load the punt supports first hand experience of an buoyancy force and to encourage them to talk about their experiences and make links to their previous work on the directions of forces.

What to Prepare

  • A cardboard punt, from the template (see below)
  • An ice-cream tub of water, or equivalent
  • A set of 10 gram masses

What Happens During this Activity

Pupils make up their punts and place them carefully on the surface. Then, using the scale on the side of the punt – and loading the punt evenly – they plot a scatter graph (as the data is collected, naturally) to show how the depth varies with the load.

The depth is a rather good proxy for the volume of water displaced. It would of course be better if the punts were perfect cuboids, but aesthetic considerations were considered more important.

We think it's a good idea to be very clear that there is a clear pattern to be found, and that skilful measurement will confirm it, perhaps like this:

Teacher: There's a very clear pattern here, and I'd like you to take great care with the measurements to see if you're good enough to make a graph that shows it very cleanly.


Download the support sheet / student worksheet for this activity.

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