6.0 Potential energy $\left( {\Delta U} \right)$

6.1 Potential energy $\left( {\Delta U} \right)$ is negative of the work done by conservative forces.
6.2 Types of potential energy
6.3 Law of conservation of mechanical energy

The energy possessed by a body or system by virtue of its position or configuration is known as the potential energy.

Potential energy is defined for conservative forces only.

As we know that the conservative force is the negative gradient of potential energy. Therefore, $$\overrightarrow F = - \left( {\frac{{dU}}{{dx}}\widehat i + \frac{{dU}}{{dy}}\widehat j + \frac{{dU}}{{dz}}\widehat k} \right)$$ or $$dU = - \overrightarrow F .d\overrightarrow r $$

Note: Potential energy is not an absolute parameter but it is a relative parameter. It means we measure potential energy at any point with respect to a reference point where we assume the potential energy to be zero.

Let us understand better with the help of an example.

In Fig. 18(a), the ground is chosen as reference. So, the potential energy of ground $(PE_g)$ is taken as zero. Therefore, the potential energy of man standing at a height $H$ is, $PE=mgH$.

In Fig. 18(b), height $H$ is chosen as reference. So, the potential energy at height $(PE_H)$ is taken as zero. Since the man is standing at height $H$, so the potential energy of man is also zero.