（214? As shown in the figure, two blocks A and B, which are connected by light springs and have a mass of 2kg, rest on the smooth horizontal ground and have a mass of 4kg.

obtained by the law of momentum conservation: mCv=(mC+mB)v1,

the * * velocity of A, B and C, taking the system composed of the three as the research object and the velocity direction of C as the positive direction,

obtained by the law of momentum conservation:

② For A, I=mAv2- from the momentum theorem, and

I=6kg? m/s；

a: ① the maximum elastic potential energy of the spring is 12J；; ?

② the impulse of the spring to a is 6kg? m/s．