Here's a mechanics problem that seems pretty straightforward, but I can't get anywhere on it. You have a system of six rods arranged in a regular hexagon, connected by hinges at each vertex, giving some non-rigid structure. Now you apply a force to one of the rods in a direction perpendicular to it, towards the center of the hexagon. This will have the effect of both adding to the total momentum of the hexagon system, as well as squashing it. The question is, if after you apply the force, the rod you were touching gets a velocity v, what is the velocity of the opposing rod? Even a hint on how to approach this would be appreciated.