One of my favorite toys to take to presentations and to get kids attention in the classroom is the toilet paper cannon. And, while it isn't really a cannon, it does shoot a stream of toilet paper across a room and cover people with a white blanket of fun. You can't imagine how excited a room full of elementary students will get when they get covered by a stream of toilet paper. And, best of all, the toilet paper cannon is simple to make and is useful for teaching important concepts in science including Bernoulli's Principle, the same concept that explains how an airplane is able to fly!
How to Build a Toilet Paper Cannon from a Leaf Blower
(Click the links to find the supplies on Amazon.com)
Fasten the handle of the paint roller to the top side of the leaf blower tube with the hose clamps or duct tape.
Slide a roll of toilet paper onto the paint roller so that the overhang of the toilet paper roll faces the opening of the leaf blower tube.
Turn on the leaf blower and let the toilet paper fly!
The Science of the Leaf Blower Toilet Paper Cannon
In order to understand how the toilet paper is able "fly" in the stream of air, you must first understand Bernoulli's Principle. Bernoulli's Principle states that a fast moving fluid (in this case the "fluid" is the air) creates an area of lower pressure than the slower moving air around it.
Another important concept to understand is that wind always flows from an area of high pressure to low pressure as the differences in pressure try to equalize. As the leaf blower is turned on and the air rushes out of the blower tube, an area of very low pressure exists at the fast moving air. The air around the opening of the blower tube is attracted toward the fast moving air because of the low pressure. This is what causes the toilet paper to be lifted into the stream of air and, due to friction caused by the air molecules on the toilet paper and the "pushing" action of the moving air, the paper is pulled away from the leaf blower and it unrolls!
This fun demonstration outlines the same physics of how airplanes are able to fly. An airplane wing is shaped so that it is nearly flat on the bottom but is curved on the top. As the plane moves forward, the air underneath the wing can pass easily below the wing but the air on the top of the wing must speed up to go over the top of the curve. This faster moving air over the wing causes an area of low pressure. The air around this zone of low pressure rushes toward the top of the wing (zone of low pressure) helping the wing to have lift and carry the airplane into the air.
Keep on Learning!
Looking for more information on Bernoulli's Principle? Watch my video "Floating Balls - Bernoulli's Principle Visualized" on YouTube.