I am very mystified by how piston and piston rings work (obviously they do). My questions are related but are in 3 parts: 1. What is highest pressure of the gas/liquid in a particular piston? (race car engine, construction machines...) and what is the approximate pressure in Kpa? 2. With the amount of liquid pressure that has to be contained by the piston ring against the wall of the piston how does it not prevent the piston from moving up and down due to the friction? 3. Can the piston seal be square or linear versus circular or is that the most efficient shape for pistons? thanks - sorry for the generality of the quesitons.