Hi, perhaps a similar thread already exists, but I was not able to find it... 1. The problem statement, all variables and given/known data Two masses m_1 and m_2 are connected by a spring with spring constant D. This setup is attached to the ceiling by a rope. We cut the rope. What happens? 2. Relevant equations The center of mass is given by z0 = (z1*m1 + z2 * m2) / (m1 + m2) The acceleration right after cutting the rope of the upper mass m1 is given by a1 = (1 + m2/m1)*g And the acceleration of m2: a2 = 0 How are the equations of motion in our center of mass system? 3. The attempt at a solution Find the equations of motion. Find the frequency of harmonic oscillation.