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;