1. The problem statement, all variables and given/known data A 2.00 kg object on a horizontal frictionless surface is attached to a spring with a spring constant 1000 N/m. The object is displaced from equilibrium 50.0 cm horizontally and given an initial velocity of 4.0 m/s away from the equilibrium position. (a) What is the frequency of motion? (b) What is the initial potential energy of the block-spring system? (c) What is the initial kinetic energy? (d) What is the amplitude of oscillation? 2. Relevant equations F = -kx F = ma [itex]\omega[/itex] = √(k/m) T = 1/f f = [itex]\omega[/itex]/2[itex]\pi[/itex] PE = 0.5kx2 KE = 0.5mv2 3. The attempt at a solution (a) So I said: T = 1/f → T = 2[itex]\pi[/itex]/f → T = 2[itex]\pi[/itex]√(m/k) I subbed in my values and got T = 0.28s Then I got f from f = 1/T and got f = 3.57s-1 (b) From PE = 0.5kx2 I got PE = 125J (c) From KE = 0.5mv2 I got KE = 16J (d) Its the amplitude part here that I got stuck. Could anyone clarify if my methods for the other parts were correct and point me some direction for part (d). Any help is much appreciated.