Letting d d represent the maximum displacement, the extremes of the block's motion are at position a, where x = − d x=−d, and at position c, where x = d x=d. at what point in the motion is the speed of the block at its maximum?

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •