1. The problem statement, all variables and given/known data Two masses slide freely in a horizontal frictionless track and are connected by a Spring whose force constant is k. Fid the frequency of oscillatory motion for this system. 2. Relevant equations My professor posted the solution but I am having trouble understanding everything that he did. according to the solution, the first step is defining the Force equation as F = -k(x2 - x1 - deltaXe) where deltaXe is the equilibrium separation. x1 is the distance to the center of mass of m1 from some point to the left of m1. x2 is the distance from that point to the center of m2. so that x2-x1 equals the distance between the center of m1 and m2. 3. The attempt at a solution the distance between the atoms at which the force on each atom is zero. Is the force repulsive (atoms are pushed apart) or attractive (atoms are pulled together) if their separation is (b) smaller and (c) larger than the equilibrium separation is this the distance between the two masses when the spring is neither compressed nor stretched? Wouldn't that just be x2-x1? so the the Force would be 0?