1. The problem statement, all variables and given/known data A particle with a mass of 65 g is moving with simple harmonic motion. At time t = 0, the particle is at its extreme positive displacement of 18.0 cm. The period of the motion is 0.600 s. Find the vecocity of the particle at t = 1.35 s 2. Relevant equations (1). ω=2∏/T or (2). ω=√k/m (3). x=Acos(ω∏+δ) (4). v=-Aωsin(ω∏+δ) 3. The attempt at a solution First question: to find ω, why don't I get the same answer for both equations 1 and 2? With equation 1 I get 10.47 (which I think is correct) and with eqn. 2 I get 7.45. Second question: How do I find the phase change for this problem? I tried to set the displacement equation equal to zero at t=0 and im getting ∏/2 but it seems that the only way to get the correct answer for the problem is to have zero phase change.