Using just air pressure – not compressed air – you can accelerate a ping pong ball to amazing speeds. Fast enough to rip through a soda can.
The cannon is a long PVC tube loaded up with a ping pong ball. To fire it off, both ends are sealed with a single layer of clear tape. Next, a vacuum pump is used to remove most of the air from the cannon tube. When the tape nearest the ball is ripped open (punctured by a knife) 14.7 pounds per square inch of air pressure rushes in and slams into the ball. With no air molecules in front of the ball, it can accelerate to speeds of nearly 300 miles per hour.
Of course if the ball does not rip through the can, you can always rip a soda can in half this way.
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