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Question

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.

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Solution

a)

The total energy and momentum of both the bodies is conserved and it is not applicable for each individual body in the case of an elastic collision.

Thus, the statement is false.

b)

The internal forces are balanced so, there will be no work due to internal forces on a body but the external forces have the ability to do work on a body. Therefore, the total energy of a system will be changed due to external forces on a body.

Thus, the statement is false.

c)

In the case of conservative force, the work done in the motion of a body over a closed loop will be zero and it is not applicable for every force in nature.

Thus, the statement is false.

d)

In an inelastic collision, there will be always a loss of energy in the form of sound, heat etc. so the final kinetic energy will be always less than the kinetic energy of the system.

Thus, the statement is true.

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