Hi
For 1. i think this is how you do it
aceleration=-n^2x = -4x
therefore, vdv/dx = -4x
fvdv = -4fxdx
v^2/2 = -2x^2 + c
v=0, x = 4
therefore c = 32
factorising gives v^2 = 4(16-x^2)
hence, when x = 0, v^2 = 64, therefore v = 8 when x is at the origin
for 2. period = Pi = 2Pi/n...