How to weigh a floating object without scales

  • When objects float on water the force keeping the object afloat is called upthrust and this balances the weight of the object.

  • When something is placed in the water, the water that moves out of the way. We say the object is displaced.

  • For floating objects the weight of displaced water is equal to the weight of the object.

Find out how to weigh an object without scales

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What is upthrust?

When objects float, they push water out of the way. We say the water is displaced.

The water pushes back with a force we call upthrust.

The water continues to be pushed out of the way until the upthrust equals the weight of the object.

Using upthrust to find the weight of an object

If the water that is displaced is weighed, we find it has the same weight as the object that is floating.

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