Broom Ball Physics

When thinking about how best to introduce Newton’s law and the study of force in his physics classes, Dan Nightingale decided to take a show-not-tell approach. In the hallway just outside his classroom, Nightingale marked off with blue tape an obstacle course. To the uninitiated, it looked a bit like a wonky hopscotch grid. “I wanted students to experience the relationship between force and acceleration in order to discern their own kinesthetic understanding of it before we delved into the conceptual realm,” said Nightingale. 

This lab allowed his students to feel the force it took to make a change to the speed of a ball. Unless the broom acted on it, the bowling ball retained its velocity (speed and direction). When a force was applied in one direction, the ball would change its rate of acceleration (speed up or slow down) in that direction. Using only the bristles, students attempted to guide the ball through a series of intentionally designed obstacles to test out various concepts related to changing velocity as force was applied. The “no touch zone” required students to apply enough force to get the ball through the 1.5-meter span. Too little and the ball sputtered to a stop and too great, it overshot its mark. The “spin cycle” introduced the concept of gravitation related to supplying inward force on an object in orbit. The trick according to Nightingale was to keep the ball on the inside while guiding it around the circle. “Zig-zag alley” expressed using force to change direction while still moving the ball forward. The activity developed the relationship between pushes to changes in motion and using only the bristles allowed for continuous force. Nightingale added an additional element and divided students into teams, which competed for the best overall time.

Back in the classroom, Nightingale led a debrief session and set the stage for further study. He subtly guided the way they thought about the exercise by reframing terms such as forward and backward motion as positive and negative force, and introducing related concepts such as inertia. The lesson capped off with each student writing up a lab report with a velocity/time graph.
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