A block of mass M is placed on the top of a bigger block of mass 10 M as shown in figure. All the surfaces are frictionless. The system is released from rest, then the distance moved by the bigger block at the instant the smaller block reaches the ground :

Explanation

I the bigger block moves towards right by a distnce X, the smaller block will move towasrds left by a distance (2.2m-X). Taking the two blocks together as the system, there is no horizontal exterN/Al force on it. The centre of mass which was ast rest initially, will remain at the sme horizontal position.
thus, ` M(2.2m-X)=MX`
or, `2.2m=11x`