Answer: The Earth.
- A The book
- B The table
- C The Earth
- D The ground
Correct answer: C. The Earth
Explanation: By Newton's third law, the book pulls the Earth upward with a force equal to the book's weight.
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.