Flying Toilet Paper – How to Make a Toilet Paper Launcher

How Does It Work

This is a wonderful example of Bernoulli’s Principle. In 1738, a Swiss mathematician, Daniel Bernoulli, studied the relationship between the pressure and velocity of a fluid. The Bernoulli Principle states that the pressure of a liquid (in this case, air) falls as its velocity increases. Increasing the velocity over the surface of the paper, lowers the pressure of the air pushing on it.

When you blow across the top of a roll of toilet paper, you lower the air pressure at that point. However, there’s higher pressure under the flapping paper. That’s why the paper lifts up. The same is true for the leaf blower but on a much more powerful scale.

In other words, Bernoulli found that the faster air flows over a surface, the less it pushes on that surface which means it has a lower pressure. The moving air from the leaf blower flows over the top of the toilet paper creating a lower pressure than the surrounding air pushing upward on the bottom side of the toilet paper. The toilet paper is lifted because there is a sufficient number of air molecules striking the lower side of the paper to overcome the downward pull of gravity and the lower air pressure on the upper side.

Real World Application

Airplanes fly because of Bernoulli’s Principle. Air rushing over the top of a curved airplane wing exerts less pressure than air moving against the flat, underside of the wing. So, the relatively higher air pressure beneath the wings provides the upward force, or lift, that enables airplanes, birds, kites, and sail planes to fly.