Push Me Pull You centre of mass motion

[Maybe_Memorie]

Homework Statement

Two identical blocks of mass m are attached via a massless spring of
spring constant k. The length of the spring in equilibrium is l. The
system moves on a frictionless horizontal plane.

With one block resting against a wall, the two blocks are pushed to-
gether, so that the spring gets compressed until its length is l/2, and
then released.
Find the motion of the centre of mass of the system after it is released.
Note: You should distinguish the two phases in which the block to the
left (i) is in contact with the wall and (ii) has lost contact with the
wall.

Homework Equations

F = ma
F= -kx

The Attempt at a Solution

I just need a hint on how to get startedwith this one please.

 

[tiny-tim]

Hi Maybe_Memorie!

I assume you can do the part where there's still contact with the wall (ie, by pretending that the block is fixed to the wall )?

ok, find the normal reaction from the wall …

when that's zero, contact will be lost, and from then on you can assume that the wall isn't there!