simple harmonic motion --> amplitude independent of mass? I know that acceleration is directly proportional to displacement, but opposite in sign, and that acceleration and displacement are related by the square of the frequency. But i was wondering if amplitude is independent of mass in simple harmonic motion? So for a spring hanging from the ceiling if i double the mass of the object hanging from the ceiling will the amplitude change? What about for a pendulum? I was under the impression that if i increase the mass the amplitude will decrease and amplitude would increase when i take mass off, but then i hit this problem in ExamKrackers Physics 1001 #742 (MCAT Book) and it says that since the force on both sides of the simple harmonic motion are proportional to the mass, the acceleration, and thsu the distance aka amplitude, will remain the same when the mass is increased or decreased. Mind you this simple harmonic motion is using friction on either side to keep it moving back and forth but I still would have thought it would have been decreased. According to the way they present their explanation I would conclude that in pendulums the amplitude would be independent of mass as well, since the restoring force is mgsin(theta). In springs, howver, the force is F=-kx so an increase in mass would decrease the amplitude.. Can someone please clarify this for me??