Savchenko Problem 4.3.13
Physics · mechanics
Problem
A wide jet of liquid of thickness h falls at angle with velocity v onto a plane. Into which jets does the falling jet disintegrate?Intuitive explanation
The key is momentum conservation in a fluid jet collision. When the jet hits the plane at an angle, its momentum component perpendicular to the surface is absorbed, but the parallel component drives the fluid sideways. The incoming jet must split into two outgoing jets that conserve both mass and momentum—one deflected in each direction along the plane. The angle and speed of these jets depend on how the incoming momentum is redirected by the surface.
Intuitive explanation
The key is momentum conservation in a fluid jet collision. When the jet hits the plane at an angle, its momentum component perpendicular to the surface is absorbed, but the parallel component drives the fluid sideways. The incoming jet must split into two outgoing jets that conserve both mass and momentum—one deflected in each direction along the plane. The angle and speed of these jets depend on how the incoming momentum is redirected by the surface.