Answer: 2.4 m/s.
- A 2.4 m/s
- B 1.6 m/s
- C 0.4 m/s
- D 3.0 m/s
Correct answer: A. 2.4 m/s
Explanation: Momentum: 8 = 2v<sub>1</sub> + 3v<sub>2</sub>. Restitution: v<sub>2</sub> - v<sub>1</sub> = 0.5×4 = 2. Solving gives v<sub>2</sub> = 2.4 m/s (and v<sub>1</sub> = 0.4 m/s).
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.