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The Simpsons Physics (1): Pianos and Angular Momentum



So The Simpsons is one of my favorite shows of all time for it's hilarious characters and plots, and interesting story. Now cartoons are not always known for their strict following of the laws of physics (because sometimes it's just funny how fake it can be), but this particular scene I am about to analyze does a pretty good job of demonstrating a key concept: conservation of angular momentum.

In this scene, a student (Ralph) is in great peril, and so Principle Skinner attempts to save him by sending a message, however, this escalates the situation as it leads to a giant crate at the docks dropping grand piano's. First, lets analyze the physics of these falling pianos. The crate appears to be tilted up at an angle of 45 degrees with the horizontal, meaning that the piano's are accelerating down the crate at about 6 m/s/s (assuming some friction). However, what is comical is that there appears to be an infinite supply of pianos as we see 20 something pianos fall out of the too small crate. Assuming a max amount of 20 pianos, and each piano at 5443 kg, the tension in the rope supporting the crate would have to be 1,100,000 N!!! 

Lastly, the Principle demonstrates conservation of angular momentum by running in a circular path around the crate. The crate then reacts and moves in the opposite direction. Because Skinner has an angular momentum in the clockwise direction, by conservation of momentum, the crate moves in a counterclockwise direction. This is also a representation of Newton's third law that for every force there is an equal and opposite reactionary force. Off course, Skinner's mass is so puny compared to the crates, it would not pin nearly as fast, but nonetheless, still hilarious. 



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