1. The problem statement, all variables and given/known data A 150g mass on a 2.2m long string is pulled 6.6° to one side and released. How long does it take for the pendulum to reach 2.8° on the opposite side 2. Relevant equations I don't know 3. The attempt at a solution I don't know where to start. I was thinking using energy but we don't have the equation for harmonic motion energy only works for springs. The other way I thought was to use x=Acos(ωt), v=-ωAsin(ωt), and a=-ω2Acos(ωt) but I can't get the right answer.