Cartesian Diver Toy

Make your own Cartesian Diver Toy!

 

Fill a 2 liter bottle to the top with water, drop the diver in and close lid tightly.

He will float at the top.

Squeeze the bottle (very hard, you might have to help your little one… I leaned into making it more buoyant than normal to combat the plastic absorbing lots of water) and hold it for a moment, the diver will drop to the bottom.

Release your grip and he will shoot back up to the top.

Repeat until your hand gets tired!

 

A little explanation of what is happening (courtesy of ChatGPT because my hand is sore from all the failed prototypes….)

 

The physics behind a Cartesian Diver revolves around these key concepts:

• Buoyancy:
  • An object will float if its weight is less than the weight of the fluid it displaces.
  • This is governed by Archimedes' Principle.
• Density:
  • Density is mass per unit volume.
  • Objects with lower density than the surrounding fluid float.
  • Objects with higher density sink.
• Pressure:
  • Pressure is force per unit area.
  • In a fluid, pressure increases with depth.

Here's how it works:

1. Initial State:
   • The diver floats initially because the air trapped inside it makes it less dense than the surrounding water.
2. Squeezing the Bottle:
   • When you squeeze the bottle, you increase the pressure on the water inside.
   • This pressure is transmitted equally throughout the fluid (Pascal's Principle).
3. Air Compression:
   • The increased pressure compresses the air trapped within the diver.
   • This reduces the volume of air inside the diver.
4. Increased Density:
   • With less air and the same mass, the diver's overall density increases.
5. Sinking:
   • Since the diver is now denser than the surrounding water, it sinks.
6. Releasing the Pressure:
   • When you release the pressure on the bottle, the pressure on the water decreases.
7. Air Expansion:
   • The air inside the diver expands again due to the reduced pressure.
8. Reduced Density:
   • With more air, the diver's overall density decreases.
9. Floating:
   • The less dense diver floats back up to the surface.

In essence:

The Cartesian Diver demonstrates how changes in pressure can affect the buoyancy of an object by altering its density.

 

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