Answer: mv 2 /L - mg.
- A mv<sup>2</sup>/L + mg
- B mv<sup>2</sup>/L - mg
- C mg - mv<sup>2</sup>/L
- D mv<sup>2</sup>/L
Correct answer: B. mv<sup>2</sup>/L - mg
Explanation: At top: T + mg = mv<sup>2</sup>/L (both toward center). So T = mv<sup>2</sup>/L - mg.
Free-body diagram of a block on an incline: weight (mg) resolves into mg sinθ along the slope and mg cosθ into the slope, balanced by the normal force N and friction f.
Concept context
Newton's three laws, friction, circular motion, and free body diagrams.