A block of mass 0.25 kg is connected to a spring with a spring constant (k) of 35 N/m. It is oscillating on a frictionless horizontal surface. It's speed as it passes through equilibrium is 1.04 m/s. What is the total energy of the system? I know that E=0.5(k)(A)^2. I just can't figure out the Amplitude. I know I can do it. I just don't know what kind of equation to use to get the amplitude. I have tried using x=A cos (wt) but that wasn't right. I have also tried vmax=A(k/m), that wasn't right either. I'm confused.