Demo Details: Eggs & Broom
The paper cylinders are made from eight and a half by eleven sheets of typing paper. They are rolled to be eight and a half inches tall and the diameter needs to be small enough so that an egg will not wedge in the end yet large enough to stand holding the egg atop. We thought it might be more dramatic to use taller cylinders and it is, but two problems are introduced. First, they are much harder to stand on end and balance an egg atop. Second, if the board does not fly out fast enough the bottom edge of the cylinders stay in contact with the board and during toppling give the eggs a backward push causing them to miss the beakers.
The board works best if it is lightweight and to facilitate this we used eighth inch fiber material. We use 1,000 ml beakers for our shows and the film, but much smaller diameter glasses can be used in that the fall of the eggs is straight down. The broom is nothing special, just and old-fashioned standard broom with long bristles that can be bent over (with your foot) and will spring the handle forward with some force. Empty is empty, water is water and the cereal is Rice Crispies. On the cereal side almost all will work, but we liked the Rice Crispies because the egg plows down in and we are trying to make the point that given some distance (or time) to stop allows the forces on the egg to be greatly reduced. As we talk about this we set the Rice Crispies beaker on the stage and drop and egg in from standing height-it is still unbroken.
There is a trick to setting up the demo. The handle of the broom needs to hit the over hanging board first and the edge of the table second. This allows the edge of the table to prevent the handle from making contact with the glassware. To picture this the bent bristles are a bit under the table and the board is not only hanging over the beakers, but also extending past the edge of the table. When aligning the paper cylinders look in both directions to be sure they are directly above the centers of the beakers. This demo falls into a class that Jack and I call surefire and easy, just give it one or two practices (use tennis balls etc.) and you’re good to go.
In talking to students during shows we turn this experiment sideways and relate it to riding in a car during a frontend collision. Bottom of the beaker becomes the windshield and the egg is your head. No seat belt, no air bag is likened to the empty beaker. Beaker with water is an airbag without a seatbelt and Rice Crispies is seatbelt plus airbag. There is some good video of crash dummies sliding over an airbag and making significant contact with the windshield due to not having a seatbelt in place. So, if you are riding in a car and you want to be as safe as possible wear your seatbelt and hopefully you have airbags. If not, from this experiment, the only other way is to fill you car with Rice Crispies!!