On our grade 11 physics exam, there was a question asking for the minimum velocity of a jet in order for it to produce a sonic boom (the temperature of the air was given, so the speed of sound in the situation was known). According to our textbook, a sonic boom is produced only after the jet's velocity exceeds the speed of sound, so using some set theory I showed that there was no solution, as there is no smallest number greater than a given constant. However, the teacher didn't like this answer and refused to give me any marks, or discuss the question with me. Out of curiosity (I don't intend to continue arguing with her), is there anything wrong with my argument in classical mechanics? P.S. This is my first post, so I apologize in advance if this is in the wrong sub-forum. This was a question arising from school, but it's a perfectly valid classical mechanics question and I'm not asking for help on homework etc.