Answer: Perpendicular to motion.
- A In direction of motion
- B Perpendicular to motion
- C Against motion
- D At 45 degrees to motion
Correct answer: B. Perpendicular to motion
Explanation: W = F x d x cos(theta). When theta = 90 degrees, cos(90) = 0, so work done = 0.
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.