Statement-1:Comets move around the sun in elliptical orbits, the gravitational force on the comet due to sun is not normal to the comet's velocity, but the work done by the gravitational force over every complete orbit of the comet is zero.
Statement-2: Gravitational force is a conservative force and the work done by a conservative force over a closed path is always zero.

Answer the following: a) The casing of a rocket in flight burns up due to friction. At whose expense is the heat required for burning obtained? The rocket or the atmosphere? b) Comets move around the sun in highly elliptical orbits. The gravitational force on the comet due to the sun is not normal to the comet's velocity in general. Yet the work done by the gravitatonal force over every complete orbit of the comet is zero. Why? c) An artificial satellite orbiting the earth in very atmosphere loses its energy grdually due to dissipation against atmospheric resistance, howerver small. Why then does its speed increase progressively as it comes closer and closer tothe earth? d)In fig i) the man walks 2m carrying a mass of 15 kg on his hands. In Fig ii) he walks the same distance pulling the rope behind him. The rope goes over pulley, and a mass of 15 kg hangs at its other end. In which case is the work done greater?

Work Done By Gravitational Forces

Is work done by a non conservative force always negative ? Comment.

Statement I : Comets revolve round the Sun only in long elliptical orbits. Statement II : A comet develops a tail when it gets close to the Sun.

Is it true for every force in nature that the work done by it on the undergoing motion in a closed loop is always zero?

A planet is revolving round the sun in an elliptical orbit. The work done on the planet by the gravitational force of sun is zero

Assertion : The work done by the spring force in a cyclic process is zero. Reason : Spring force is a conservative force.