1. The problem statement, all variables and given/known data Two elastic bars are joined. A step wave is coming in from left. Derive the shape and magnitude of the reflected wave if the right bar is approximated by a rigid body (point- mass) that is free to move in the axial direction. 3. The attempt at a solution I have problem with the boundary conditions, I know that a free will reflect the wave as a tensile wave and that a fixed end (eg wall) will reflect the wave as a stress wave. But what if the "wall" could move? Should i use the conservation of momentum and investigate or is there a equation that can describe this?