A simple harmonic oscillator consists of a block of mass 4.50 kg attached to a spring of spring constant 170 N/m. When t = 1.90 s, the position and velocity of the block are x = 0.188 m and v = 3.150 m/s. (a) What is the amplitude of the oscillations? What were the (b) position and (c) velocity of the block at t = 0 s?

Question

emmatassone · Answer

a good advice is always draw the situation to facilitate the resolution of the problem:
|dw:1442779438369:dw|
 
Then use the kinematic equation that describes the harmonic simple movement:
$$X(t)= Acos(wt+\phi), A=amplitude, w=\sqrt{\frac{ k }{ m }}$$ 
$$v(t)=A.w.\sin(wt+\phi)$$
If you know calculus, you should be able to see that the velocity is the derivative of X(t).
Finally to get what you want evaluate in those functions and you will get the info about the amplitude and phi.