1. The problem statement, all variables and given/known data A particle is in simple harmonic motion with period T and with position as a function of time given by x(t) = A cos(wt+ø). At time t = 0 the particle is at x = A/2 with positive velocity. The next time it is at the same position is ___? 2. Relevant equations w/(2pi)=1/T 3. The attempt at a solution So I know the cosine of the argument has to = 1/2 for the position to be half the amplitude. The first time this happens is at t = 0. This implies the phase constant ø is pi/3. The next time the cosine argument is a positive 1/2 is when the argument equals 300 degrees. Therefore: wt + pi/3 = 5pi/3 wt = 4pi/3 t = 4pi/(3w) w = 2pi/T t = 4pi/[3(2pi/T] = 4pi/[6pi/T] = 2T/3. The answer however is t = T/3.