Upthrust
Forces and Motion | Properties of Matter

Experiencing buoyancy forces

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Floating balloons.

The purpose of this activity is to give pupils first hand experience of a 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

  • Some party balloons
  • A bowl of water or water in a sink – or outside

What Happens During this Activity

Invite pupils to float the inflated balloon on the water, then to gently push the balloon into the water. The volume of the balloon is such that a considerable force upwards will be experienced by the pupils. This is such a simple exploration, yet one that few pupils will have experienced first hand.

Upthrust
is a special case of Force
appears in the relation Upthrust = Weight of Displaced Liquid
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