Steve Spangler’s Flying Toilet Paper
Bernoulli’s Principle explains how air pressure differences combine for an awesome demonstration.
It’s amazing what you can do with differences in air pressure. A tasty drink flows through a straw from a glass up to your mouth. A vacuum pulls dirt from the floor and drops it into a bag. A kite floats on a gentle breeze. A 900,000 pound (410,000 kg) airplane lifts into the air like a bird. Toilet paper flies off the roll and… wait! Toilet paper?! Do it right and you’ll see air pressure differences empty a roll of toilet paper in seconds!
“The Ellen DeGeneres Show,” A Very Good Production, E W Scripps Company
Ping-Pong® is a registered trademark of Parker Brothers. All Rights Reserved.
- Handheld hair dryer
- Ping-Pong® ball
- Empty toilet paper tube
- Full roll(s) of toilet paper
- Leaf blower
- Balloon (penny inside it)
- Beach ball
- Stick (broom handle, or piece of PVC pipe work great)
- Safety glasses
- Adult supervision
NOTE: The video is a segment from The “Ellen DeGeneres Show” featuring an appearance by Steve Spangler. The portion that applies directly to this activity starts at 1:42. But heck, just watch it all… it’s really fun!
Before you go after launching toilet paper, however, do these activities first so you know the science behind the fun and how to handle the setup.
Hold or support the dryer so it’s stable and doesn’t wobble with the airstream pointed directly up. If you have the option, use the “cool” setting on the blow dryer.
Place the Ping-Pong ball into the stream of air and let go. Watch the ball until it’s very steady in the moving air. It won’t take long.
With the ball pretty much in one place, slowly tilt the hair dryer left and right and watch the ball move with it. How close to horizontal can you get?
Make sure the ball slips easily through the toilet paper tube.
Turn on the hair dryer, place the ball in the stream, and hold the empty toilet paper tube in the moving air well above the ball. Slowly lower the tube toward the ball in the air. At a certain point, the ball is pushed into the tube and zips upward through the tube. It leaves the airstream and falls to the ground.
Slip a penny into a balloon, inflate the balloon, and tie it off.
Turn the hair dryer on high again. If you have them, place two Ping-Pong balls into the moving air and watch them dance.
Replace a ball with the inflated, weighted balloon in the air flow. What happens if you move the hairdryer slowly? quickly?
Grab the full roll of toilet paper. Hold the roll so the paper goes over the top of the roll and falls on the side away from you. Unroll a few sections and blow straight across the top of the roll. Surprisingly, the dangling paper lifts upward as you blow. Now, use the hairdryer to blow over the top of the roll. The lifting paper is the reason airplanes fly.
For this Step, the hair dryer probably doesn’t have enough oomph. You need a really big “dryer”: try a leaf blower.
Grab the stick and slide the full roll of toilet paper over it so the paper unrolls away from you. Turn the blower on high and let the air move over the top of the roll of toilet paper. The roll will be empty in a few seconds! Be sure to clean up the fun when you’re finished.
How Does It Work
The floating ball is a wonderful example of Bernoulli’s Principle. Bernoulli, an 18th-century Swiss researcher, discovered something quite unusual about moving air. He 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 hair dryer flows around the outside of the ball. That makes a lot of moving, low pressure air around the ball. Directly above the ball, however, the air is not moving very much so it has a higher pressure. It tends to hold the ball in place. Gravity pulls the ball downward as well while the blowing air from below the ball forces it upward. This means that all the forces acting on the ball are balanced and the ball hovers in midair above the hair dryer.
As you tilt the hair dryer you make the ball follow the stream of air. Bernoulli’s principle says that the fast moving air around the sides of the ball is at a lower pressure than the surrounding stationary air. If the ball tries to leave the stream of moving air, the stationary, higher pressure air holds it in. The ball floats in the air as long as you move it slowly.
When you place the empty toilet paper tube into the airstream, the air is pushed into a smaller area inside the tube where it moves even faster (the Venturi Effect). The pressure inside the tube becomes even lower than that of the air surrounding the ball and it gets pushed up and out of the tube.
The penny in the balloon adds mass to the balloon. It’s possible you may not need it but odds are that an empty balloon will simply blow away in the airstream.
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. The air pressure drops for a much farther distance out above the paper and the higher pressure stays in place father out, too. That’s why the paper from a leaf blower launch curves upward for most of the distance it covers.
Take It Further
The addition of a leaf blower is definitely taking it further. If you can manage this option, you’ll have a lot of fun. Using a leaf blower in place of a hair dryer, you can float larger objects like beach balls and maybe volleyballs.
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.