Smoke Ring Launcher / Vortex Machine
Years ago, toy manufacturers like Wham-O used to sell air blasters that
sent bursts of air sailing across a room to the surprise and delight of any
innocent victim. With a little practice, it was quite easy to shoot a cup off of
someone's head from 20 feet away. Whether you buy one from your
favorite toy store or make your own, you'll have a blast with this retro
science toy.
Materials
•5 gallon bucket
•Bungee cord
•Plastic shower curtain or thick plastic sheet
The science toy is called an AirZooka
Experiment
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.
Experiment From Steve Spangler Science
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