On Tom’s desk was his windup car, a baseball, a rock of the same size, and a few balloons. Written on the blackboard was the aim of the day’s lesson: “What are the three laws of motion?” In groups of twos and threes, his sophomore science students sauntered into the room, tossing their books onto the desks, and chatting aimlessly with their friends. As was their custom, Barry and Manny examined the items on their teacher’s desk in a desultory manner. By the afternoon, high school students often exhibit academic fatigue through impatience, boredom, inattention, and irritability. Tom knew he had to act fast to maintain their interest.
Accordingly, the skinny young science teacher started the lesson with a jolt by releasing an inflated balloon toward the open door. The whooshing balloon darted into the hall, to the amusement of his students, who reacted vociferously.
Before Tom could stop him, Barry grabbed a balloon, blew it up, and sent it out of the room on a similar trajectory.
“Who can explain what happened here?” Tom asked the class.
Riner raised his hand. “Action and reaction. The air is forced out of the balloon backward, and the balloon moves forward in the opposite direction.”
“Very good. It’s called Newton’s third law of motion: For every action, there is an equal and opposite reaction,” Tom stated.
“I know Fig Newton. He’s the guy that dropped the two rocks from the Leaning Tower of Pizza,” Barry replied.
“Actually, it was Galileo who did that experiment from the Leaning Tower of Pisa, which proved that all objects fall at the same rate of speed due to gravity.”
“Whatever. Show us the windup truck already,” the irrepressible teenager responded.
Tom sent the windup car across his desk, which did not impress his students, who had seen that notorious car earlier in the semester. Then, as the science teacher sent the car on its way across his desk, he dropped the rock on it.
“So what happened here?”
“The car slowed down because of the added weight of the rock,” Wendy quickly responded.
Next, Tom sent the baseball rolling across the desk with a slight push. Then he sent it rolling faster with a harder push.
“Who can summarize the first experiment with the car and the second experiment with the baseball in a law of motion?”
“The acceleration of an object varies inversely with its mass and varies directly with the applied force,” Wendy answered.
“That’s absolutely correct, Wendy,” Tom replied. “One more thing, folks. I’m going to roll the baseball across my desk. What property of matter is shown here?”
“That round objects tend to roll forever?” Manny responded.
“Well, yes. But let’s make it more general.”
“That an object in motion stays in motion. And an object at rest stays at rest,” Ronnie answered.
“That’s absolutely correct, Ronnie,” Tom replied.
“How come whenever a girl answers a question right, you say it’s absolutely correct. But when a boy says something right, you barely acknowledge it,” Barry complained.
“That’s because I like girls better than boys.”
“That’s discrimination. I’m going to report you to the principal, Mr. Stout.”
Ignoring the pesky student’s complaint, Tom turned to the board. He instructed his reluctant pupils to take out their science notebooks. The following conclusions of the day’s lesson were written on the blackboard.
Isaac Newton’s Three Laws of Motion
First Law: An object at rest tends to stay at rest, and an object in motion tends to remain in motion.
Second Law: An object’s acceleration varies directly with the applied force, and varies inversely with its mass.
Third Law: For every action or force, there is an equal and opposite reaction or force.
As the class drew to a close, Tom took out a match-head–filled, tin-can rocket. As expected, the rocket immediately grabbed everyone’s attention. Years ago, Tom had set off a similar rocket, aiming it toward the hallway. Unfortunately, the rocket slammed into Mr. Stout’s ample backside, to the joy of his students and the consternation of the grumpy school administrator.
Experience being the wisest teacher, Tom aimed the rocket toward the ceiling. Lighting the fuse with a match, the rocket seemed to tremble momentarily before it whizzed upward, smashing into the classroom’s high ceiling. The class roared in delight as the room filled with sulfur fumes. Amazingly, the tin can rocket stuck onto the ceiling tile, where it remained for many weeks, as a reminder of their teacher’s fun lesson on Newton’s laws of motion.
“Now that was a truly awesome practical experiment! You should do more stuff like that, Mr. Haley,” Barry yelled.
“If I did something like that every day, I’d lose my job,” Tom replied as the class exited the room joyfully. Besides the jammed rocket, the room had filled with sulfurous fumes that wafted along the hallways.