If you happen to be a police officer and write someone a ticket for not coming to a complete stop at a stop sign, you better hope that person isn’t a college physics professor. Because if he is, you might have to go to court against someone like Dmitri Krioukov. Krioukov received such an infraction and decided to use that opportunity to put his knowledge of physics to use.
In his hearing, the professor presented a paper called The Proof of Innocence. Here’s his argument: “If a car stops at a stop sign, an observer, e.g., a police officer, located at a certain distance perpendicular to the car trajectory, must have an illusion that the car does not stop, if the following three conditions are satisfied: (1) The observer measures not the linear but angular speed of the car; (2) The car decelerates and subsequently accelerates relatively fast; and (3) There is a short-time obstruction of the observer’s view of the car by an external object, e.g., another car, at the moment when both cars are near the stop sign.”
Basically, that’s a fancy way of saying that it’s the driver’s word against the police officer’s word. Krioukob argued that he did come to a full and complete stop, but his car’s linear velocity was obscured by the cop’s perspective because another vehicle came into his line of vision at the same moment. His defense veven included an entire series of graphs. Whether he actually persuaded the judge or just confused him, he won. Oh, and his paper has since been published in a physics journal.