Which expression represents kinetic energy?

• A. 1/2 m v^2
• B. m g h
• C. m v
• D. m v^2

Answer: (A)

Kinetic energy is the energy of motion, depending on both how heavy something is and how fast it’s moving. The standard expression is 1/2 m v^2, which shows why speed has a squared effect and why heavier objects at the same speed have more energy. The other expressions relate to different ideas: m g h is gravitational potential energy (energy due to height in a gravity field), m v represents momentum (the quantity of motion), and m v^2 isn’t the standard kinetic-energy form (it equals twice the kinetic energy when tied back to KE through p = m v). So the correct representation of kinetic energy is 1/2 m v^2.