Hannah's Build-It
The Cartesian Diver
Materials:
-
2 liter soda bottle
-
Plastic pipette
-
Metal nut (non-corrosive)
-
Water to fill your 2 liter/pipette
-
Something deep enough to test your pipette's density
How to make your own:
-
Slide the corrosion-free nut onto the pipette far enough where it will not slide off on its own
-
Cut the tip of the pipette to where roughly 1/2'' of the pipette extends past the nut
-
To make the pipette dense enough to float on the surface but not sink fill it with water.
-
Fill the pipette bulb about half way so it will hardly float on the surface
-
Tip: Turn the pipette over and tap it to remove some of the extra air into the tube of the pipette.
-
Squeeze the bulb of the pipette to remove some of the water and air to then draw up some more water into the pipette. When you add more water to the pipette more air will be brought in as well. Which you will want to move up to the top of the pipette where there is a bubble of air.
-
Your diver should just barely float at the top of the water's surface.
-
You can now place your diver into the bottle, be sure to fill the bottle to the very top with water.
-
Adjust the amount of water in the bottle as needed. You may need to add more water if it is too difficult to move the diver with the pressure of just your thumb.
Here is a video of Jeff Goodman making a Cartesian Diver to help you build yours!
So How's It Work??
A Cartesian diver helps demonstrate two opposing forces. Buoyancy is the upward force on an object and causes things to float, while gravity is the downward force on an object and causes objects to sink.
Meaning:
Upward force = Bouyancy
Downward force = Gravity
As you squeeze the bottle it creates an increase in the pressure inside the bottle. This increase of pressure is experienced throughout the entire bottle and causes the air inside the pipette to be compressed. This makes the pipette more dense and its bouyancy decreases making it sink as gravity takes over. When you stop squeezing the bottle the bouyancy of the pipette increases as it becomes less dense and the object floats.
-
Density=How much STUFF in How much SPACE
-
Less dense=more likely to float
-
If an item is more dense than what it's in it sinks.
-
If it is less dense than what its in, it floats.
-
Squeezing makes the dropper more dense!