Mechanical energy is the sum of which two forms of energy?

• A. Kinetic energy and thermal energy
• B. Elastic potential energy and chemical potential energy
• C. Mechanical energy equals mass times velocity
• D. Potential energy and kinetic energy

Answer: (D)

Mechanical energy is the total amount of energy associated with an object's motion and its position. It combines kinetic energy, which comes from moving, with potential energy, which depends on where the object is in a force field (like gravity or a stretched spring). In a frictionless system, this total stays the same because energy simply shifts between motion and position. That’s why the sum is kinetic energy plus potential energy. The other ideas mix in energy that isn’t part of the mechanical total—thermal energy is heat energy from microscopic motion, which isn’t counted in mechanical energy; mass times velocity gives only kinetic energy; and while elastic or chemical potential energies are types of potential energy, the overall mechanical energy is their combination with kinetic energy.