Newton’s third law – for every action, there is an equal and opposite reaction – is best explained with a jet bottle.
Katie Teed, a junior at Seneca High School, hammers a nail into a block of wood set on the chest of Jerry Magraw, senior laboratory technician in the School of Science.
Jerry Magraw built this one. He set the bottle on its side, tied it to a little skateboard and poured in a bit of methanol. He touched a lighter to the bottle’s mouth and – WHOOSSHH!!! – a long blue cone of flame roared out. The rocket shot forward.
The students applauded. Magraw, the senior laboratory technician in the School of Science, already had moved on; in the next half hour, he would launch a Pringles can, freeze a racquetball, fire a pingpong cannon and lie on a bed of nails as a student hammered into a block of wood on his chest.
“It does keep them interested,” he said.
That’s the point of Physics Day, which brought 80 high-school science students to Penn State Behrend on Nov. 20. School teams compete to solve three experiments. They race jitterbug robots and try to determine the speed of sound in air. It reminds them that science can be fun.
“These kids are the cream of the crop,” said Paul Ashcraft, lecturer in physics and coordinator of the program. At the end of the day, he awards the Knacke Cup, a trophy that goes home with the top-scoring team. North East High School took it for a second consecutive year.
The competition is friendly. “Part of it is getting them to learn a little about science,” said Jonathan Hall, senior lecturer in physics. (His role in the Magraw show: yanking a tablecloth without disturbing the place-settings. That illustrates Newton’s first law, which involves objects at rest.) “And part of it is getting them to meet other students who are just as interested in science as they are.”
The high-energy demonstration show is a bonus, a reward for all those hours in honors and Advanced Placement classes. Magraw and the others skewer balloons, throw eggs into bed sheets and use a leaf-blower to unspool a roll of toilet paper, which drifts in a long ribbon across the room.
That last trick is an example of Bernoulli’s principle, which holds that an increase in velocity in a gas will decrease its pressure. Like all theories from 1738, it is far more fun when you see it being done.