That is, va = 43 VB.

(2) When the spring returns to its original length, the rising height of A is h = x0cotα = 43x0.

Let the elastic potential energy when the compression of the spring is x0 be Ep, and the mechanical energy of the system composed of A, B and the spring is conserved.

Ep= 12mvA2+ 12？ 2mvB2+mgh= 179mvB2+43mgx0。

(3) If the accelerations of objects A and B are zero and the interaction force is F, then

The stress analysis of A is as follows: Fsinα=mg.

The stress analysis of B is as follows: Fcosα=kx.

It can be seen from the above that x = mgkcot α = 4mg3k.

Answer: (1) When the spring has just returned to its original length, the speed of A is VA = 43 VB.

(2) The elastic potential energy of the spring compressed by xo is 179 MVB2+43 MGx0.

(3) When the kinetic energy of two objects is maximum, the compression of the spring is 4mg3k. ..