Yancheng Medical Equipment Spring

When A, B, and A are just separated, the six accelerations of B subjected to gravity mg and constant force F and B are zero, and the six accelerations of A are also zero, indicating that the elastic force has an upward elastic force on A, which is in balance with gravity and the spring is in a compressed state. So, AB is wrong.

When C, B and A were just separated, the elasticity of the six springs was mg, but the elasticity of the six springs was mg when I was at rest, so the elasticity decreased by △ f = mg. When two objects move upward by six distances, the elastic force decreases △ six =h, which is obtained by Hooke's law: k=△F△ six = mgh. So, C is correct.

D. Before B and A were separated, the whole AB was taken as the research object, with constant gravity, decreasing elasticity and decreasing resultant force, and the whole AB was undergoing variable acceleration. So, d is wrong.

So choose C.