The parts of a hydraulic machine are moved by liquids; pneumatic machines are moved by a gas, e.g., air. A hydraulic system is one with a pipe that is filled with a liquid, e.g., oil, and a piston that moves back and forth inside the pipe. As the pushed liquid forces the piston inside the pipe to move, power is transmitted from one end of the pipe to the other end.

This project is a simple hydraulic machine powered with water pressure. The water comes from a central reservoir and goes into a pipe. The bag expands and forces the piston up as water begins to fill the plastic bag. This action can raises heavy objects.
 

 
MATERIALS NEEDED:

1. Airtight plastic bag
2. Large plastic bottle
3. Scissors
4. Plastic tube
5. Tape
6. Plastic funnel
7. Spray can lid
8. Heavy book
9. Pitcher of water

FIRST, cut the top off the large plastic bottle, making sure the plastic bag is airtight. Wrap the neck over the end of a piece of plastic tube and seal the bag to the tube with tape.

NEXT, attach a funnel to the other tube end and make a hole at the bottle's base. Feed the bag and tube through so that the bag sits in the bottom of the bottle.

THEN, put the spray can lid on top of the bag and sit a heavy book on top of the bottle. Raise the tube's funnel end up and SLOWLY pour water into it. What happens now?