Smoke Rings Create a small blast of air or a giant ring of smoke! email to friend
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It's easy to make your own air blaster using materials that you can easily find at the hardware store. Start by finding a 5 gallon plastic bucket (about $3 in any hardware store). Carefully cut a 2 to 3 inch hole in the bottom center of the bucket. The only thing left is to stretch a membrane across the top of the bucket. Believe it or not, a piece of clear plastic shower curtain works great. Just stretch a piece of the shower curtain over the top of the bucket and secure it in place using a bungee type cord. That's it! When you lightly hit the shower curtain with your hand or the end of a stick, an invisible blast of air shoots out of the hole. Just aim the air cannon at someone or something across the room and send a blast of air with a whack of the membrane.

How does it work?

This activity demonstrates the fact that air occupies space. As the rubber sheet is pushed into the interior of the bucket, the volume decreases and pressure increases. The increase in pressure forces some of the air out of the hole. The velocity at which the air leaves the bucket is inversely proportional to the diameter of the hole; the smaller the hole the greater the velocity of the air. Students may have experienced a similar phenomenon as they constrict a garden hose to increase the velocity of the flowing water.

The proper name for the air cannon device is vortex generator. The "ball" of air that shoots out of the cannon is actually a flat vortex of air, similar to rings of smoke blown by a talented cigar smoker.

Additional Info

Smoke Ring Launcher - Start by finding a round, plastic trash can. Rubbermaid makes trash cans that work quite well. Carefully cut a 25 cm hole in the bottom of the trash can. The only thing left is to stretch a membrane across the top of the can. I stretch a piece of clear plastic show curtain over the can and secure it in place using a bungee type cord. That's it! When you lightly hit the show curtain, a transparent ring of spinning air shoots out of the hole. Just aim the air cannon at someone or something across the room and send a blast of air with a whack of the membrane.

How can you make the invisible ring of smoke visible? With a little smoke, of course. The best smoke rings are made by filling the trash can with theatrical smoke. Smoke machines (foggers) are commonly used in stage productions. Check to see if your theater department has one, or see if you can borrow one from the disc-jockey who plays for your school dances!

The best smoke rings are made by gently tapping the shower curtain. A hard smack results in a fast, blast of air that is difficult to see. The flying vortices are best seen against a dark background with light coming from either side.

A vortex is generated because the air exiting the bucket at the center of the hole is traveling faster than the air exiting around the edge of the hole. That swirling or vortex motion can be observed if a little smoke is blown into the bucket just before giving the rubber membrane a gentle push.