The ideal pendulum is formed by a sphere E ofmass m, attached to one end of an ideal string whose otherO end is fixed to the Earth. The sphere is released fromfrom rest, from the horizontal position shown in thefigure. When it reaches the lowest point of its trajectory it crasheswith block B, of unknown mass, which is locatedResting. Suppose that this collision can occur from onlytwo forms: it can be perfectly elastic orperfectly inelastic.

E B