Harmonic Motion

[dudgey]

I have a physics problem that I'm stuck on! Its a position vs time graph of harmonic motion of a horizontal mass/spring system. The question is "where is the acceleration greater than 0?". The graph starts at point A (at the origin), goes to B (above the x axis), down to C (on the x axis), down to D (below the x axis), and up to E (on the x axis).

I thought the answer should be between B&C and D&E because these (I think) would correspond to when the mass was going from a point with no kinetic energy to a point with maximum kinetic energy. This can't be right because the choices are A&B, A&C, C&D, C&E, B&D, both A&B and D&E. What's going on? Thanks :)

[Pyrrhus]

The problem might because the question asks greater than 0

[dudgey]

Ok, I guess I should just think of it more that the second derivative is acceleration....

[Pyrrhus]

Go look in your Textbook there should be a graph comparing

Position vs Time

Velocity vs Time

Acceleration vs Time