Why should the amplitude be small for a simple pendulum experiment?

Explanation

When amplitude of the vibrating pendulum is small then angular displacement of the bob used in simple pendulum is small. Here, the restoring force `F=mgsintheta=mg theta=mgx//l` where x is the displacement of the bob and l is the length of pendulum.Hence, `Fpropx`. Since F is directed towards mean position, therefore the motion of the bob of simple pendulum will be SHM if `theta` is small.