In order to understand the perspective of conservative force, we consider a block of mass "m", which is projected up a smooth incline. Here, interactiion involves gravitational force. The force due to gravity, opposing the motion, is mg sinθ along the incline. Let us consider that the block travels a total length "L" along the incline before returning to the point of projection.

A block projected on a smooth incline plane |
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Work done by gravity during motion in upward direction is :

Work done by gravity during motion in downward direction is :

Thus, we find that :

This condition, when stated in general terms, specify whether the interacting force is conservative or not. In general, let

Work done along closed path is zero :

We summarize important points about the motion, which is interacted by conservative force :

- The object regains initial motion (kinetic energy) on return to initial position in a closed path motion.
- Conservative force transfers energy "to" and "from" an object during a closed path motion in equal measure.
- Conservative force tansfers energy between kinetic energy of the object in motion and the potential energy of the system interating with the object.
- Work done by conservative force is equal to work done by it on reversal of motion.
- Total work done by conservative force in a closed path motion is zero.