Answer: 36 W.
- A 12 W
- B 16 W
- C 36 W
- D 48 W
Correct answer: C. 36 W
Explanation: P = I<sup>2</sup> x R = 9 x 4 = 36 W.
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.