1. The problem statement, all variables and given/known data The motion of a simple pendulum is only approximately simple harmonic. How small should the amplitude should be for the approximation to hold good?. Obtain the general expression for the time period of a simple pendulum. How much does the actual time period differ from the approximate time period when the amplitude is 15 degree? 2. Relevant equations 3. The attempt at a solution On obtaining the period of oscillation using SHM, we approximate sin(a)=a in radians. I was thinking of keeping it as sin(a). Any help with the first question? The amplitude one.