A2 . A pendulum of mass m and length I is initially at rest at an angle 0. The pendulum then swings down and collides elastically with a stationary block of mass M. The block slides along the surface and eventually stops when it encounters a rough patch of length |Ad) . m- M Assume that m = 1. 7kg, L = 0.80m, 0 = 670, M = 2. 8kg and |Ad| = 0.55m. a) Calculate the speed of the block immediately after the elastic collision. [2 points] b) What is the coefficient of kinetic friction of the rough patch? [3 points]