LUDION

MATERIALS:
-A plastic bottle
-Transparent tube of a pen
-Insulating tape and scissors
-Elastic rubber
-Clips

MAKING OF:
1. Fill the bottle with water.
2. Cover one hole of the pen with insulating tape. If the pen has got a lateral hole, it has to be covered too.
3. Join the clips to the pen with the elastic rubber, in order to float with the open hole inside the water.
4. Close the bottle.

When you press the bottle, you can see how the pen goes down to the bottom of the bottle. When disminising the pressure, the pen goes up again.

EXPLANATION:
Pascal's and Archimedes' Principle allow us to explain the experiment.
Before pressing the bottle, the pen floats due to its weight is smaller than the thrust power made by the water.
When you press the bottle, the pressure is transmitted to the bottom of the pen and the water enters in the bottom, so its produces an increasement of the pen's weight (the aire is sustituted by the water)When the weight is higher to the thrust, the pen sinks.
When you stop pressing, the water comes off and the pen goes up.

by Julia and Begoña