Deborah Germany

PT Training

Pressure Demonstrations

Crushing a Can & Breaking a Yard Stick

Purpose:  To demonstrate air pressure

Materials: 

Crush Can

2 – empty aluminum coke cans

1 – hot plate

1 – tongs

1 – clear tub with water

Yard Stick

1 – soft wood yard stick

2 – paper book covers

1 – metal rod or other object to strike the yard stick

1 – atmospheric bar

(These two demos can be done at the same time.)

Procedure:

1.  Put enough water in the coke cans to cover the bottom of the cans. 

2. Place the cans on the hot plate to heat the water to boiling.

3. While waiting for the water to boil, place the yard stick on a smooth, flat surface and

     cover it with the two paper book covers.

4. Leave about 4-5 inches of the yard stick over the table.  Take the metal bar and hit the

     end of the yard stick. The yard stick will break off.

5.  Talk about the pressure per square inch of a column of air and how it presses down the

     book covers.

6.  If the water is boiling in the can, take the can with the tongs and turn it over so that

     the open end of the can  is under the water .  The can will be crushed by the air

     pressure in the room.

7.  Repeat step 6 with the second can.

8.  Pass around the classroom an atmospheric pressure bar to demonstrate how much a

     square inch of air weighs.

You can use these two demonstrations to introduce the unit on pressure.