The performing professor. Physics students pay attention when he walks over hot coals

IT'S early in the afternoon and Jearl Walker has already walked barefoot over hot coals, dipped his hand into molten lead, and successfully snatched a tablecloth out from under a half dozen liquid-filled glass beakers. His audience seems to have enjoyed the show. But Dr. Walker is not a performer in a traveling circus. He's the head of his university's physics department and a widely respected teacher and author. He also must be one of the most unusual professors in the United States.

Jearl Walker is part teacher, part showman, and something of a folk hero to physics students at Cleveland State University (CSU) here.

Professor Walker has taught at CSU for 13 years and boasts that his physics courses are the most demanding at the school. ``I give more homework than anyone,'' he says. While his students support that claim they add that the course is also one of their favorites. ``His class makes you want to learn,'' says sophomore Greg Lacrosse. ``He keeps me constantly interested in the material.''

For many non-science majors, the prospect of studying physics is about as enjoyable as an IRS audit. Walker acknowledges this and works hard to pepper his lectures with gags and stunts. ``I'll try a great many things to wake students up,'' Walker says. ``While they're awake I try to teach them as fast as I can. I usually have to wake them up about every 10 minutes.''

Walker seems to enjoy those wake-up calls, using corny gags and off-beat stunts to drive home that day's lesson plan. In one, he strips off his shirt and lies between two boards covered with hundreds of nails (points up), while a student puts a large concrete block on his chest. Another student slams a 12-pound sledge hammer into the block. Walker says, ``It really doesn't hurt much,'' because much of the energy is absorbed by the concrete block, which shatters from the blow. The bed of nails proves safe because Walker's weight is properly distributed. It's an effective lesson in the principles of physics.

But this stunt-teaching is not without risks. In a stunt calling for Walker to dip his wet hand into bubbling molten lead, the vaporizing moisture serves as insulation against burns - unless the lead accidentally gets caught under a fingernail, a lesson Walker learned during one demonstration.

While it's hard to find a colleague critical of Walker's teaching methods, few copy his techniques. Walker thinks ``that's fine.'' ``I would never insist that teachers be like me. I'm just trying to break the monotony of a professor talking `golden' words to the class, chalking `golden' words on the board.''

``If every physics teacher could somehow get 50 percent of Jearl Walker's love and enthusiasm for the subject,'' says Jack Wilson, executive director of the American Association of Physics Teachers, ``a lot more people would study physics.'' He adds: ``[Walker] has demonstrated the importance of graphic demonstrations which highlight [how much] fun physics can be.'' But Mr. Wilson concedes that some of Walker's stunts raise eyebrows and concern that students will be injured in trying to duplicate them. Walker says he cautions students not to try any of the dangerous stunts themselves.

In addition to teaching, Walker also writes a popular monthly column in Scientific American, and contributes regularly to a weekly Canadian radio show. He's also the author of a widely used physics textbook, ``The Flying Circus of Physics With Answers.'' In it he answers such questions as why the haze in a city appears brown and why a cat is likely to land on its feet.

James Rogers edits Walker's column in Scientific American and is often surprised by Walker's suggestions for topics. ``Walker has got people interested in physics who never would have been before. I like that he's not conventional and I think maybe there should be more professors like him,'' says Rogers.

Mary Kay Johnson is a junior at CSU who looks forward to Jearl Walker's class. ``As a freshman, one of the first things you hear about is his course,'' Ms. Johnson says. She still can't forget the time Walker broke bricks with his bare hand. ``When you see a stunt like that, it's hard to forget the course material,'' Johnson says. ``Those stunts assure that nearly every lesson sticks in your mind.''

Jearl Walker began teaching at CSU after completing undergraduate work at the Massachusetts Institute of Technology and earning a PhD at the University of Maryland. During his first faculty year, his teaching style was informal but much the same as that of his colleagues. It was during his second year that he faced his first large lecture class. Walker realized that he'd have to change his style to communicate with the 150 students peering at him and began to blend in a theatrical touch.

``It was a scary situation. I thought the students might just walk out of the class,'' Walker says. ``So I would do voice changes, act out skits, and incorporate stunts into my teaching.'' Up until that point, Walker considered himself shy and not ``a funny guy.'' But his students' enthusiastic response spurred him on and their test results confirmed that they were learning the necessary material.

Props play a key role. During a recent class, the room is silent as Walker appoaches a heavy cement block dangling from a 7-foot rope tied to a beam. He stands with his back to the wall and pulls the block to his face before releasing it into a wide swing. The students seem to hold a collective breath as the pendulum races back toward Walker's face, missing his teeth by only inches. The professor explains the physics that makes the block stop short of hitting his face. The stunt is rewarded with something few teachers ever receive from their students - applause.

(If you're still wondering how Walker pulls off the ``barefoot over hot coals'' routine - and don't try this yourself - here's the secret: When he does the stunt he's nervous, and the bottoms of his feet perspire. When his feet touch the coals, part of that sweat vaporizes, which forms a layer of insulation between his flesh and the coals. In addition, most of the coals' heat energy is inside, not on the surface of the coals. By moving quickly with moist feet, the ``mind over matter'' trick is brought down to everyday physics.)