A hamster that I own that is mechanical in nature. With a simple flick of a button it runs on its wheel or wherever you it wants. I does not gnaw incessantly on it's cage.
The study of the force, propulsion, tension, work, and energy conservation of shit down the toilet. Also deals with the: inertia, angular acceleration, and period of the turd when it circles and floats down the bowl. Then after that something that has to deal with thermodynamics and sewage.