Which of the following is NOT a form of potential energy?

Mechanical energy is the correct choice as it is not solely a form of potential energy. Rather, mechanical energy encompasses both kinetic energy (the energy of motion) and potential energy (the energy stored due to an object's position or configuration). In contrast, elastic potential energy, gravitational potential energy, and chemical energy are all forms of potential energy, indicating the energy stored within an object due to its position, state, or structure. For example, elastic potential energy is stored when an object is stretched or compressed, gravitational potential energy is related to an object's height above the ground, and chemical energy is stored within the bonds of molecules. Since mechanical energy includes both kinetic and potential energy, it cannot be categorized as one specific type of potential energy.