A person of mass M is, sitting on a swing of length L and swinging with an angular amplitude θ0. If the person stands up when the swing passes through its lowest point, the work done by him, assuming that his center of mass moves by a distance l(l<<L), is close to;
(1) mgl (1 + θ02)
(2) mgl
(3) mgl(1 + θ20/2)
(4) mgl(1 – θ20)