Which expression represents kinetic energy?

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

Answer: (C)

Kinetic energy is the energy an object has because it is moving. It depends on both mass and speed, with speed mattering more because it is squared. The formula 1/2 m v^2 captures exactly this relationship: half the mass times the square of the velocity gives the energy of motion. The other expressions describe different concepts: m g h is gravitational potential energy (energy due to height in a gravity field), m g is weight (a force), and m v is momentum (not energy). So the expression that represents kinetic energy is 1/2 m v^2.