Answer: 8 kg.
- A 4 kg
- B 8 kg
- C 16 kg
- D 32 kg
Correct answer: B. 8 kg
Explanation: KE = (1/2)mv<sup>2.</sup> 64 = (1/2)m(16). m = 64/8 = 8 kg.
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.