A simple pendulum of length L is set into oscillation with a small initial angular displacement. Ignore air resistance unless stated.
(i) State the principle that relates the total mechanical energy of the pendulum at any two instants during its swing when dissipative forces are absent.
(ii) Describe qualitatively how the kinetic and potential energies of the pendulum vary during one complete oscillation.
(iii) Suppose a small amount of energy ΔE is lost due to friction at the pivot in every swing. Explain how this loss affects the maximum angular displacement and the speed at the lowest point in successive oscillations.