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The main objective of these experiments is to explain the Archimedes' Principle, which states that any body completely or partially submerged in a fluid at rest is acted upon by an upward force. The size of the force is equal to the weight of the water displaced. Using this principle, students would be able to tell why some things sink and float.
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Materials needed for the submarine 1. plastic pen top 2. 16oz. of water 3. modeling clay 4. 16oz. clear plastic bottle |
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Strategy
1. Stick a small piece of clay on to the pen top. This is the submarine.
2. Put the submarine into a glass of water. Remove or add modeling clay until the submarine floats upright.
3. Completely fill the bottle with water. Put the submarine in and screw the top on tightly.
4. Squeeze the bottle and the submarine will float up and down.
The squeezing will cause the pressure inside to go up and any gas trapped inside the bottle (like the air inside the pen cap) will shrink. This will change the buoyancy on your "submarine" from neutral to negative and it will sink to the bottom. When you release the pressure the air will expand and the sub will rise.
Materials needed for a Cartesian Diver
1. 16oz. plastic bottle
2. 1 drinking straw
3. 1 bottle top full of modeling clay
4. 16oz. of water
Strategy
1. Fill a plastic bottle with water right to the top.
2. Make a diver from a straw, paperclip and clay. Cut the straw 2 inches long, open up a paperclip, take the straw and put it on each end of the paperclip, apply clay round the end of the paperclip.
3. Test that it floats in a glass of water. Add clay until it only just floats.
4. Once the diver is just floating, put it in the bottle of water.
5. Screw the top on the bottle.
6. Squeeze the bottle gently. The diver should sink. Stop squeezing the bottle and it should rise. A diver like this is called a Cartesian diver.
