Can you give me a link where I can find a simple explanation of the formula of the period of a pendulum? As far as I know, if the angle is 3°, the tension on the rope is g/ cos 3 and the horizontal T = 9,8 * tan 3 (0.0524) = 0.5 N. Is this the only force to consider? Can you tell me how to proceed to find the time the bob reaches the vertical position? supposing l = .98 m , I know (from PE) that final v there is 16 cm/s and space travelled is 5.13 cm, but I cannot use the formula: t^2 = 2 s/a: since it is not an incline, a is not constant, is integration the correct procedure? of what function? what is the formula for an arc? Thanks, as I said, a link will do, how to find the exact value? how do we end up with √l/g?.