Spring with mass on horizontal surface

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 = 4J



(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.