Physics in the real world

Toss a basketball in the air. Watch it come down.

It’s a perfect illustration of free fall, a basic physics concept, and it’s one of the first lab projects teacher Jim Scheidegger assigned the five students in his summer school physics class. They gently toss basketballs over motion detectors connected to laptop computers. The goal is to produce graphs of the basketballs’ acceleration and velocity. After a false start—one student neglects to catch the ball and it crashes into the motion detector—the computer screens begin to display sets of irregular lines that, to the untrained eye, resemble the peaks and valleys of an electrocardiogram. “Are you happy with that data? Want something prettier?” Scheidegger asks. “Try it again.”

Scheidegger, a former NMH faculty member who returns to teach in the summer school, is on a mission to make physics more straightforward—more real—to teenagers. “You throw a ball up in the air. Who hasn’t done that?” he asks. “Physics should not be the nightmare it is often viewed to be. We want students to walk out of a physics class and see what they’ve done in class as part of the world they live in.”

But puzzling questions come up during the lab. How can the ball be tossed and still be in someone’s hands? How can a ball stop at the top of its flight and still be accelerating at 9.8 meters per second? A student grimaces, and Scheidegger nods. “Yeah, that bothers you, doesn’t it? It should bother you. We need to work these bothersome concepts into our heads until they make sense; they’re the foundation of how the world works.”

A couple weeks later, the students have moved from gravity to propulsion and from basketballs to water rockets. With a one-liter plastic bottle, lots of duct tape, a computer simulator, and their new knowledge of projectile formulas, the students designed rockets and predicted their maximum height and range. They experimented. They tinkered. Then they launched behind Memorial Chapel, using a bicycle pump to put the “engines” under 80 pounds of air pressure per square inch. With one hard yank on a string, the rockets flew over the football field. A crowd of spectators oohed and ahhed.

Despite the show, launching a rocket is a lot like tossing a basketball, at least from a physics perspective. “We’ve got the same up-and-down motion,” Scheidegger explains. “We add the horizontal component, and then we’ve got the movement that all objects make going through the air.” Once the fuel that propels the rocket—in this case, water and air—runs out, the rocket behaves much like the basketball, or any other projectile in free fall.

One of Scheidegger’s students, Naomi, has already taken an honors physics class. She’s studying physics again so the concepts and formulas “make more sense in my mind,” she tells Scheidegger after the ball-tossing lab. “You see how it all comes out right?” he asks her. “Yeah,” she says. “It’s scary right.”