1. The problem statement, all variables and given/known data Three identical point masses of mass m each are placed at the vertices of an equilateral triangle and joined through springs of equal length and spring constant k . The system is placed on a smooth table. If the masses are displaced a little towards the centroid of the triangle then time period of oscillation of the system is : A)2π√(m/k) B)2π√(m/2k) C)2π/√(m/3k) D)2π√(m/5k) 2. Relevant equations F = -k x ω = √(k/m) 3. The attempt at a solution Consider one mass which is displaced from the mean position by x units. The two forces acting on it are k*x* cos(30 Degree) each inclined at an angle of 60 Degrees. That would mean that the force acting on it is actually (3/2)*k*x, or the equivalent spring constant is (3/2)*k. But that gives an weird time period which isn't in the options!