Answer: 2000 N.
- A 800 N
- B 1000 N
- C 2000 N
- D 4000 N
Correct answer: C. 2000 N
Explanation: P = F x v. F = P/v = 40000/20 = 2000 N. This equals friction at constant speed.
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.