State if each of the following statements is true or false. Give reasons for your answer.
a) In an elastic collision of two bodies, the momentum and energy of each body is conserved.
b)Total energy of a systm is always conserved,no matter what internal and external forces on the body are present.
Work done in the motion of a body over a closed loop is zero for every force in nature.
d) In an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the sytem.

Explanation

False .In an elastic collision of two bodies , the total momentum and total energy of the system remain conserved but not that of each body .
(b) False . The external forces acting on a system can increase or decrease the total energy of the system .
(c ) False , Work done in the motion of a body over a closed loop is zero only if the body moves under the action of conservative forces ( like gravitational forces or electrostatic forces ) and not when the forces are non - conservative ( like frictional forces ) .
(b) True .In an inelastic collision , a part of kinetic energy of the system usually changes into some other forms of energy .