[quote:0748e969ef="Anonymous"]From what I learned in physics. The equation for the period of a simple pendulum is T=2(pi)(L/G)^1/2. Which means constant length should result in constant period. However I change the angle of release on the pendulum and the period changes!!??.[/quote:0748e969ef] The period of the pendulum is almost constant if the amplitude if small (small angle vibration) However, the period will change very small amount when the angle increase. It only increase less than 2% for 20 degree (relative to vertical line).