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Phun with a Capital P
by Harold Rodriguez

In a blatant disregard for spelling, the UF chapter of SPS (Society of Physics Students) performed their "Physics is Phun Show" for elementary school students.

As part of the physics outreach program, a handful of dedicated SPS students headed over to Lake Forest Elementary, after dragging and loading tons of gadgets and thingamajigs into The Physics Van. Like jolly old Saint Nick, they arrived on the scene and started unloading the toys. What may seem like an ordinary bicycle wheel to some is actually an amazing "physics-defying" demo for others. And those are the best kind of toys.

Top: Erica Bolin prepares to rotate in her chair by tilting a bike wheel. <br>Bottom: Two students desperately try to separate electromagnets. Top: Erica Bolin prepares to rotate in her chair by tilting a bike wheel.

Bottom: Two students desperately try to separate electromagnets.
The demos in the exhibition included liquid nitrogen stunts, squealing tubes, interfering sounds, spinning chairs, "weight-deceiving" objects, flying buckets of water, rotating pennies, electromagnets, strangely-weighted pipes, freezing batteries, expanding shaving cream, and of course the "angular momentum" bike wheel. Needless to say, the children had lots to marvel at.

The show started off with a bang as liquid nitrogen was precariously poured over the floor (precariously by professionals, of course!). The reaction was one of Oohs and Ahs, and a few chilly toes. "This is just the beginning," we said. Next came an old crowd favorite: the wheezing tubes. By spinning them around quickly, air travels up the tube (directed away from your hand) because of Bernoulli's Principle. Low pressure builds up near the faster spinning end of the tube causing the air to migrate there and resonate through the tube.

Another sound demo was the two xylophone keys of adjustable frequency. This way, when played together, one could hear variable beat frequencies. Next came the angular momentum portion of the show, starting off with having people spin in a chair. Masses were given to them, and whenever they brought the masses closer to their bodies, they spun faster, and vice versa. The kids seemed to have a good time with this one. After, they tried it with a spinning bicycle wheel. Whenever they tilted the bike wheel, they'd start rotating the chair. Like magic! Other objects were spun around (like buckets of water and a penny on the tip of a clothes hanger!).

After some demos about the distribution of weight (and its difference to mass), it was now time for Return of the Liquid Nitrogen. This demo involved putting a fully-inflated balloon into a pool of N2. Contrary to the hypotheses of the students, who thought the air escaped the balloon, the balloon decreased in size because the molecules of air inside stopped moving so quickly. The decrease in temperature caused the gas's volume and pressure to decrease. When the balloon was lifted out, the gas warmed up and expanded to blow the balloon up again. Along the same lines, a pressure chamber caused shaving cream to more than quintuple in size. Our work here was finished. The kids had an entertaining distraction from regular coursework, the teachers were happy, and our next class awaited us back at UF. Before going home, however, there was a little matter about how to dispose the left-over liquid nitrogen. We discovered that angular momentum is more useful than anticipated.