Answer: Opposite to motion.
- A In direction of motion
- B Opposite to motion
- C Perpendicular to motion
- D At 45 degrees
Correct answer: B. Opposite to motion
Explanation: W = Fd cos(theta). When force is opposite to motion, theta = 180 degrees, cos(180) = -1. W is negative.
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.