During free fall, which describes the energy transformation?

• A. Both energies increase.
• B. Potential energy decreases; kinetic energy increases.
• C. Potential energy increases; kinetic energy decreases.
• D. Both energies decrease.

Answer: (B)

During free fall, gravity does positive work on the object, turning gravitational potential energy into kinetic energy. As you drop, height decreases, so gravitational potential energy U = mgh decreases. At the same time, the speed increases, so kinetic energy K = (1/2)mv^2 increases. In an ideal case with no air resistance, the loss in potential energy exactly equals the gain in kinetic energy (ΔK = -ΔU), keeping the total mechanical energy constant. If air resistance were present, some energy would also be dissipated as heat, so not all potential energy loss becomes kinetic energy. This description matches the idea that potential energy decreases while kinetic energy increases.