Answer: 2 N.
- A 6 N
- B 4 N
- C 2 N
- D 12 N
Correct answer: C. 2 N
Explanation: Acceleration of the system = 12 / (1 + 2 + 3) = 2 m s<sup>-2</sup>. The string on the 1 kg block must accelerate only that block: T = 1 × 2 = 2 N.
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.