Answer: Third law.
- A First law
- B Second law
- C Third law
- D All three laws
Correct answer: C. Third law
Explanation: Every gravitational force has an equal and opposite partner (Newton's 3rd law). Earth pulls Moon; Moon pulls Earth equally.
g is maximum at Earth's surface; going up, it falls off as 1/r² (inverse-square); going down, it falls off linearly with depth (since only the mass enclosed within radius r contributes), reaching zero at the centre.
Concept context
Universal gravitation, orbital mechanics, gravitational potential, and escape velocity.