Answer: 24 J.
- A 12 J
- B 24 J
- C 36 J
- D 0 J
Correct answer: B. 24 J
Explanation: Common v = 12/6 = 2 m/s; KEi = 36 J, KEf = 0.5·6·4 = 12 J; loss = 24 J.
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.