Answer: zero.
- A equal to its kinetic energy
- B positive and increasing
- C negative
- D zero
Correct answer: D. zero
Explanation: Constant velocity means zero acceleration, so net force is zero and net work is zero (the KE does not change).
As a pendulum swings, total mechanical energy (KE+PE) stays constant: at the highest points A and C, all energy is potential (zero speed); at the lowest point B, all of that energy has converted into kinetic energy (maximum speed).
Concept context
Work-energy theorem, potential energy, conservation of energy, collisions.