Problem 2 (Energy conservation ) A block of mass M is lying on a stand and is attached to the spring with spring constant k. Initially the spring is not stretched and the system is at rest, see Figure. Next, the stand with the block begin to lower with constant acceleration a. After what time the block will come off the stand? What is the maximum length the spring will stretch to? a Problem 3 (Momentum conservation) The ball falls from some height with zero initial speed on the horizontal surface. All collisions between the ball and the surface are elastic. For the first t seconds, the ball has traveled distance s. How many times during this time the ball hit the surface