Submerging the Submarine

You will need:

1. 2-litre clear plastic bottle filled with water
2. Pen-cap
3. Modelling clay

Understand the science behind submarines with this simple experiment.

INSTRUCTIONS

1. Firstly, block the pen-cap opening with modelling clay. Then stick a 1-inch (in diameter) ball of clay on the bottom extended part of the pen-cap.
2. Put the pen-cap and clay contraption
   into the plastic bottle filled with water.
3. Screw the bottle-lid back onto the bottle.
4. Place the bottle on any surface.
5. Squeeze the bottle until the pen-cap
   and clay sink all the way to
   the bottom.
6. Release the bottle.
   What happens?

RESULT

As soon as you release the bottle, the pen-cap begins to ascend and floats back to the top. Any object which is denser than water will sink to the bottom while an object less dense than water will float. While the pen-cap and clay may be denser than water, the air pocket inside the cap makes it lesser in weight than water. To add to that, any object when surrounded by a liquid, gets an upthrust with a force equal to the weight of the liquid. As a result, it floats. However, when we squeeze the bottle, the air pocket is compressed making the cap denser than the water. As soon as the bottle is released, the air pocket inside the pen-cap expands again and begins to rise. A submarine functions on the same principle. The large air tanks on either side of the submarine are either filled with water to make the submarine sink or filled with compressed gas to make it float.