Information about Make a cartesian diver with Fizzics Education | Kids Science Experiments

Make a cartesian diver

Make a cartesian diver

Follow FizzicsEd 150 Science Experiments:

You will need:

A small soft drink bottle

A Plastic pipette



Two nuts to fit the pipette.

You can use a pen lid with plasticine to weight it down, but it is not as effective.

Cartesian diver science experiment - materials needed landscape

Fill the bottle with water all the way to the brim.

2 Cartesian diver science experiment - position to cut the transfer pipette

Cut off the star like components of the pipet.

3 Cartesian diver science experiment - cut pipette with metal nuts as ballast

Fit two metal nuts to the bottom of the cut pipette (or add plasticine to the pen cap).

4 Cartesian diver science experiment -correct position of pipette floating in the water

Float the cut pipette in the water and adjust the weight to allow it to float.

5 Cartesian diver science experiment - pipette floating before squeezing the bottle

Close the bottle and tighten the lid.

6 Cartesian diver science experiment - squeezing water bottle causing the pipette to sink

Squeeze the bottle and the ‘Diver Dan’ should sink, letting go he should rise.

Why Does This Happen?

This toy is also known as a SCUBA Steve or simply a Cartesian Diver.

The toy works on buoyancy. Squeezing the bottle exerts a pressure throughout the contained fluid. This pressurized fluid rises into the opening at the bottom, making the pipette heavy and sinking it. Releasing the bottle reduces the pressure around the pipette, allowing the trapped air inside the pipette to expand, increasing its buoyancy and allowing it to float.

We’ve seen this same experiment done with tomato sauce packets, biro lids and Freddo Frog packets. Really any small trapped air space can work, you just need to be able to fit it into the bottle and weigh it down to keep it floating upright. Have fun!

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