1. The problem statement, all variables and given/known data A SHM motion can be described by a=-400x. The amplitude is 8cm. Find the displacement and acceleration at a time of 2s. 2. Relevant equations x = A sin(2pi f t) x = A cos(2pi f t) a=-(2pi f)squared*x 3. The attempt at a solution Firstly I realised that 400=2pi f , so f =64Hz. But then I go stuck cos you don't know if this is a cos or sin oscillation. Im not sure where to go from here, but I just know theres a way around this. Any help?