Answer:
I started answering this before everything was erases, but briefly
W = 1/2 K x^2 so K = 2 W / x^2 = 6 * 25 = 150
Also F = - K X = 150 * 1/5 = 30 N at max extension
m = F / a = 30 /15 = 2 kg
Since max extension occurs at t = 0 you can write
x = A sin ω t
v = ω A cos ω t
a = -ω^2 A sin ω t note that there is no phase angle here
Also at .1 compression
.1 = .2 sin ω t and sin ω t = 1/2 and ω t = 30 deg = pi / 6
Substiture these values above to get velocity and acceleration when
ω t = 30 deg
