Which statement describes a common example of energy conservation in a falling object?

• A. Energy is created as the object falls.
• B. Energy increases without bound as it falls.
• C. The sum of potential energy and kinetic energy remains constant (ignoring air resistance).
• D. Energy disappears due to air resistance.

Answer: (C)

When a body falls under gravity with no air resistance, energy simply shifts from one form to another without being created or destroyed. The gravitational potential energy (mgh) decreases as height drops, while the kinetic energy (1/2 mv^2) increases as speed rises. The total mechanical energy, mgh + 1/2 mv^2, stays the same because no non-conservative forces are taking energy away. This is why energy conservation is described as potential energy converting into kinetic energy during a fall.

If air resistance were present, some energy would be transformed into heat and other forms, so the mechanical energy would not stay perfectly constant, even though the total energy (including the energy stored as heat) would still be conserved.