Hydrostatic Pressure Force "must" be perpendicular Hi, I'm taking AP Physics B and we started learning about fluids and pressure. My teacher told me that the pressure of a fluid acting in a a container only applies a perpendicular force to the sides, which doesn't make sense. If you 'zoomed in', molecules could strike the surface of the container at any angle, right? So couldn't the forces be in anything from parallel (well, not really) to perpendicular, and everything in between? Is it just a simplification or literally only the molecules that hit the surface perpendicularly that impart a force? Thanks for your time!