1. The problem statement, all variables and given/known data A small block is oscillating on a spring with a period of 3.05 s. At t = 0 the mass has zero speed and is at x = 4.35 cm. What is the magnitude of the acceleration at t = 4.30 s? 2. Relevant equations a=-Aω2cos(ωt) ω=2∏/T 3. The attempt at a solution ω=2∏/3.05=2.06 x(0)=Acos(0)=4.35=A(1)=A so:a=(t)=-4.35(2.06)2cos(2.60(4.30))=-18.3 m/s2 which I've been told is wrong. I have no idea what I'm doing wrong, I'm sure it's something painfully obvious but I just can't figure it out.