A simple pendulum is composed of a mass m connected to a string of length / that is fixed to a horizontal support, as depicted below. The angle 0 is a measure of the pendulum's deviation from the vertical. Assume the acceleration due to gravity is g. D m a. Choose a system with which to model the pendulum that is isolated (e.g. its total energy is conserved). Explain your choice of system and how you can tell its energy is conserved