Answer: 20 N.
- A 10 N
- B 20 N
- C 50 N
- D 25 N
Correct answer: B. 20 N
Explanation: Limiting friction = μmg = 0.4 × 5 × 10 = 20 N, which is the force needed to just overcome friction.
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.