1. The problem statement, all variables and given/known data A particle moves along x-axis subject to a force toward the origin proportional to -kx. Find kinetic (K) and potential (P) energy as functions of time t, and show that total energy is contant. 2. Relevant equations K = (1/2)m*v^2 P = (1/2)k*x^2 E = K+P x = Asin(wt + [tex]\tau[/tex]) v = dx/dt = wA(cos(wt + [tex]\tau[/tex]) 3. The attempt at a solution K = (1/2)m*v^2 = (1/2)m*w^2A^2(cos^2(wt + [tex]\tau[/tex]) P = (1/2)k*x^2 = (1/2)k*A^2(sin^2(wt + [tex]\tau[/tex])) But when I add these to get the total energy, the terms with t do not cancel, and so the total energy is not constant. I can only imagine then that I've done something wrong in the above, very basic steps. Any suggestions would be appreciated. Thanks.