1. The problem statement, all variables and given/known data Two chests are connected by a 15 meters long rope attached to a ceiling hook hanging 4 meters high. The chest (1) at 5 meters from the hook has a velocity of 1/2 m/s away from the other chest (2). The chests remain flat on the ground and the rope is under tension. What is the speed of the other chest? 2. Relevant equations 3. The attempt at a solution Let c1,2 be the chests, let h be the hook, let centre be the perpendicular projection of the hook on the ground. We know the distance c1-centre (right triangle) at any time (1/2 m/s). We also know the distance c1-h (right triangle), h-c2 (length of the rope), hence we know the distance c2-centre (right triangle) at any time. The time derivative of this function at t=0 solves the problem. Is there a shortcut, another approach? Can you think of any interesting physical or mathematical considerations? I don't think my solution is very satisfactory.