In the process of releasing the spring, taking the right as the positive direction, the momentum conservation and mechanical energy conservation of systems A and B are obtained from the law of momentum conservation:

mBvB-mAvA=0，

According to the law of conservation of mechanical energy:

mAvA2+ 12mBvB2=EP，

In the process of collision between B and C, the momentum is conserved, with the right as the positive direction, which is obtained by the law of momentum conservation:

mBvB=(mA+mB)v，

Simultaneous and alternative data: v = 2m/s;

A: The speed at which BC sticks together is 2m/s;