Inside Real Teaching

As the pearly yellow egg bounced upwards on the end of its elastic tether (narrowly missing the hard tile floor just a few centimeters below), the students in Mr. Applegate’s Block 4 Physics I class breathed a collective sigh of relief. The laws of physics had been proven – and so had their classmates’ understanding of them. Soon, all of the students (deemed "JumpMasters" for the duration of this lab) in the class would have their turn at the bungee jump. Or their eggs would, at least.

To demonstrate the principles of elastic and potential energy (as well as the need for exact and precise calculations), all of Mr. Applegate’s Physics I students would take part in the bungee jump, launching their plastic eggs (the "jumpers" of the experiment) from the staggering 2.67 meter height of the ceiling. Before the "jump," the students had attached their eggs to string (cut to their own specifications) which was, in turn, tied to a long piece of elastic. Depending upon the students’ mastery of several important concepts – the spring constant of elastic, the period of vibration of the egg attached to the elastic, gravity, and conservation of energy – the eggs (which were weighted down with pennies) would either fall the correct distance and bounce back up with the elastic, or fall too far and smash into a small pool of water and the tile floor below. Most of the eggs had been given interesting (and frequently fitting) monikers, such as Cool Hand Luke, Tommy, Tony Blair, and Tom Joad. Looming ominously beside the jumping area was a large collection of cracked, smashed, and otherwise mutilated eggs, which had apparently not enjoyed successful jumps. While many of the eggs did survive the experiment, the occasional (but frequently spectacular) failures were certainly the highlight of the experiment. During one jump, the knot connecting the string and the elastic quickly fell apart. In another group’s attempt, the elastic and string combination turned out to be nearly twice as long as needed, and reached to the floor when hanging from the ceiling. One egg ably survived its jump, only to smash into a table on its bounce back upwards.

Juniors in Mr. Applegate's physics class experiment  with an egg and gravity in this Bungee Egg Lab.

At the conclusion of the lab, the "JumpMasters" had to return to their usual roles as Physics I students and were given an exam on energy – although many of them would have undoubtedly preferred to attempt the jump themselves than to take the exam!