1. The problem statement, all variables and given/known data A 0.50 kg particle executes linear harmonic motion about the point x = 0.0. At t= 1.0, it has a displacement x = 0.50m and a speed of 5.0 m/s to the right. The frequency of the motion is 2Hz. Determine (a) the spring constant, (b) the amplitude of the motion, (c) the displacement as a function of time t...blah blah blah... The rest of the questions wants you to form equations and find displacements at other times which is a piece of cake. 2. Relevant equations Acos(wt+ phase) -wAsin(wt+phase) 3. The attempt at a solution Spring constant is easy - 78.87 N/m. Ok, when it is asking for amplitude I am little confused. Maybe someone can help clear it up. It says it executes linear harmonic motion at x = 0.0. Does this mean that there isn't a phase angle since it is initially at rest at t = 0s and x = 0? If there isn't a phase angle that makes solving for amplitude so much simpler since I can just set it to 0 and calculate the amplitude using the conditions at t = 1.0s. Anybody?