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Cartesian Diver - Pressure & Buoyancy Experiments
Cartesian Diver - Hook the Hoop
Materials you will need:

• Water
• Large soda bottle
• Drinking straw
• Scissors
• x1 Small sized paper clip
• x1 Medium sized paper clip
• Sink
• Plastic colored string (tube - with a hole)
• Blu tac, plastacine or play dough

This is a fun and challenging experiment!

Have fun making a Cartesian Diver and challenging yourself and others.

See if you can get the balance of weight and air pocket just right to make the diver float and then dive.

If you master this then play a game to see if you can get your diver to hook the hoop.


1.   Fill your soda bottle with water leaving just a bit of a space (gap) at the top.

2.  Cut a piece of straw 2 inches long

3.  Pull the two rounded ends of the paper clip apart slightly

4.  Bend your straw in half and push the rounded ends of the paper clip into the opened ends of the straw.

5.  Open the small paper clip to make a hook and wrap it around the center bit of the paper clip that is in the straw ends.

6.  Take some play dough and wrap it around the middle bit of the first paper clip. This is to give your diver a bit of weight. Make sure you get the balance right so that your diver will float at the top of your bottle.

7.  Cut a piece of string around 3 inches long.

8.  Roll out a good bit of play dough so that it will easily fit into the mouth of the bottle and heavy enough to sink to the bottom of the bottle.

9.  Tuck both ends of the string into this play dough securely and drop into your bottle.

10.  Screw the lid on to the bottle tightly.

11.  Place a hand or both hands around your bottle and apply a bit of pressure.

12.  Does your diver sink?

See photos below.

Have a play and see what works best. Should you apply pressure at the top part of the bottle?

Does it work better if you apply pressure at the middle of the bottle or the bottom of the bottle?

Challenge yourself and friends to see how many attempts it takes to hook the loop at the bottom?

Experiment with different materials from around the house. Come up with different types of Cartesian Divers.




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