question_answer 7)

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 system is always conserved, no matter what internal and external forces on the body are present. (c) 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 system.  

Answer:

(a) False. Total momentum and total energy of the entire system are conserved and not of individual bodies. (b) False. The external forces acting on a body may change its energy. (c) False. In case of a non-conservative force like friction, the work in the motion of a body over a closed loop is not zero. (d) True. In an elastic collision, a part of the initial K.E. of the system always changes into some other form of energy.