'Physics Circus' at U of M mixes science and stagecraft

Barrel crush
The most dramatic experiment in the Physics Circus is the collapsing barrel. Steam inside a 55-gallon steel barrel cools and condenses before outside air pressure collapses the barrel. The collapse is noisy and startled the crowd of students, as well as the photographer.
MPR Photo/Tim Post

University of Minnesota physics professor Dan Dahlberg is out to prove that physics isn't so complicated.

"Physics is interesting, it's fun and it's understandable," Dahlberg said.

Now, the real challenge. Dahlberg and a few other scientists who call themselves the Physics Force, need to win over thousands of elementary and middle school students squirming in their seats in Northrup Auditorium on the University of Minnesota campus.

But the physicists know how to keep the crowd's attention while teaching them about science. They key is to entertain them.

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Over the next several days, the university will host a "Physics Circus" that aims to interest students in physics with stunts that are fun. During the shows, a few physicists take the stage and use basic science to generally cause mayhem. They'll break stuff, shoot things out of cannons, and make lots of noise -- all in the name of science.

During a recent show before more than 2,000 students, scientists and teachers drove the young audience wild, and delivered a lesson about air pressure, by using a leaf blower to send toilet paper streaming 40 to 50 feet above the stage.

Another noisy experiment used a 10-foot long gun to shoot ping pong balls. When air pumped from a pipe by a vacuum rushed back in, a ping pong ball shot out the end, taking down a stack of soda cans in the process.

Toilet paper shoot
The Physics Force team drove the crowd of between 2,000 and 3,000 students wild by shooting toilet paper 40 feet above the stage using a leaf blower. It's a fun way teach students about air pressure and the Bernoulli Effect.
MPR Photo/Tim Post

During another, a physicist sat in a chair on wheels with a fire extinguisher. The scientist then rocketed across the stage with a stream of exhaust shooting from behind.

The lesson: for every action or force, there's an opposite reaction.

From the audience's perspective though, it just looked cool.

But the entertaining physicists really captured the students' attention with their most dramatic experiment.

A 55-gallon steel barrel, sealed up tight and full of boiling water and steam, was wheeled out onto the stage. As the steam inside cooled, it condensed back into water. But as the steam also supplied the pressure inside, the students were about to get another lesson in air pressure.

Fire extinguisher rocket
A physicist shoots across the stage like a rocket with the exhaust of a fire extinguisher. The lesson, every force or reaction results in an opposite reaction.
MPR Photo/Tim Post

"Do not take your eyes off the barrel, because this is not something that happens slowly," a scientist said.

The students didn't make a sound. But they knew something big was about to happen, as the sturdy steel barrel began to creak. And then, BAM! The barrel collapsed in on itself like a squashed soda can.

The show isn't meant to recruit future physicists, Dan Dahlberg said. Instead, scientists hope to encourage students to appreciate physics -- or at least not fear it.

"You don't have to be a card carrying Ph.D physicist to enjoy physics," Dahlberg said. "It's something everybody can enjoy and learn and understand."

Learning more about physics is something the University of Minnesota Physics Force thinks might be good for more than just students.

The group has two free shows open to the public, at 7 p.m. tonight and 2 p.m. Sunday at the Northrup Auditorium, 84 Church Street S.E., Minneapolis.