Conservation of Energy or Momentum?

1. Apr 28, 2007

Conservation of Energy or Momentum??

A mass M is attatched to a horizontal spring of force constant k fixed on one side to a rigid suppport.(Please imagine the diagram). The mass oscillates on a frictionless surface with time Period T and amplitude A. When The mass is in equilibrium another mass m is gently placed on it. What will be the new amplitude of oscillation.

My approach,
Conservation of energy
1/2 Mw(1)^2A(1)^2= 1/2 (M+m)W(2)^2A(2)^2 where w is omega.
And then on rearranging the terms i got
[A(1)/A(2)]^2 and
w(1)/w(2) on the left hand side i substituted it with (m+M)/(M) since w is inversely proportional to m.