1. The problem statement, all variables and given/known data A 0.12-kg block is suspended from a spring. When a small stone of mass 30 g is placed on the block, the spring stretches an additional 5 cm. With the stone on the block, the spring oscillates with an amplitude of 12 cm. What is the net force of the stone when it is at a point of maximum upward displacement 3. The attempt at a solution The answer is Fnet= mass of pebble x gravity. The solution says this is the case because the spring isnt moving. But shouldn't Fnet = force of gravity + force of spring? Since at maximum compression, the spring will exert a down acceleration. Just because it's not moving doesn't have to mean it isn't causing acceleration right? And when I look at the position graph and the acceleration graph of horizontal simple harmonics, the greatest magnitude of acceleration of a spring is when the spring is at maximum compression or stretch- the amplitude. If there's acceleration then there must be force? Or is this different because this is vertical? Thanks.