Momentum problem

[bluesky]

Consider a gravity free hall in which a tray of mass M,carrying a cubical ice block of mass m and edge L,is at rest in the middle.If the ice melts,what would be the displacement of the system?

 

I think it has to do with the conservation of momentum,since no external force is acting.But i cannot think further.Please help.

[bluesky]

I think I have got the answer.F=M(d^2R_cm/dt^2)=dP/dt=o

To have even a uniform motion of CM,what we need is a motion of CM from the rest.That must involve an acceleration.

Since acceleration of CM is zero,we must conclude that CM did not move at all.

Please check if I am correct.

[ronthepon]

Yes, the displacement of all the particles (the center of mass of the system will be zero.