Which is an example of kinetic energy?

• A. Water stored behind a dam.
• B. A parked car.
• C. A light bulb lit.
• D. A swinging swing.

Answer: (D)

Kinetic energy is the energy of motion. A swinging swing is currently moving through the air, so it has kinetic energy. Water stored behind a dam isn’t moving, so its energy is gravitational potential energy stored due to height (it would gain kinetic energy if it starts to flow and accelerate). A parked car isn’t moving, so it doesn’t have kinetic energy at that moment. A light bulb that’s lit uses electrical energy and emits light and heat, which isn’t kinetic energy of moving matter. The swinging swing, by being in motion, best exemplifies kinetic energy.