^Potential energy 

^Potential energy 

1. Potential energy is defined only for conservative forces.
2. Gravitation, electromagnetic, spring force all are conservative.
3. Friction is non conservative.
4. Usually a point at infinity is assigned zero value i.e. U∞ = 0
5. Potential energy can be + ve, -ve or zero.
6. Generally –ve potential energy indicates attractive forces & +ve indicates repulsive forces.