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In a system, mechanical energy will be conserved if:

In a system, mechanical energy will be conserved if: Correct Answer conservative forces act

CONCEPT:

  • Conservative Force: A force, such as gravitational force, is conservative force if work done by the force depends on the displacement only and not on the path.
    • Work done by conservative forces is zero for when the path is a closed-loop because displacement for closed-loop will be zero.
    • Potential energy or stored energy for a system or body can be defined only for conservative forces.
  • Non-conservative Force: A non-conservative force is one for which the work done depends on the path, for example, friction force.
  • Conservation of mechanical energy: According to this principle, The total mechanical energy of a system is always conserved.
  • The energy can neither be created nor be destroyed; it can only be converted from one form of energy to another form. And this is possible only if the forces doing work on the system are conservative forces in nature.

EXPLANATION:

  • According to the principle of the conservation of mechanical energy, The total mechanical energy of a system is conserved only if forces working on it are conservative forces.
  • For option 3, both forces are included conservative and non-conservative, so it is not a correct answer.
  • So the correct answer is option 2 i.e. conservative forces act.

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