What is the sign of work done in each of the following cases? Justify your answer
(a) Work done by the force of gravitation on a freely falling body.
(b) Work done by the force of gravitation when a body is lifted upwards
(c) Work done by the electrostatic force when a positive charge is moved closer to another positive charge.
(d) Work done by the electrostatic force of nuclus on an electron revolving around it.
(e) Work done by the gas enclosed in a cylinder fitted with a piston when the gas is allowed to expand.
