Newton's Third Law Illustration

Newton's third law of motion states that for every action, there is an equal and opposite reaction. A key aspect is that these forces act on two different objects.

Analyzing the Situations

Let's evaluate each option to find the clearest illustration of this principle:

• Option 1 & 3: A stone resting on the ground and a book on a table are examples of objects in static equilibrium. While gravitational force (action: Earth on object) and normal force (reaction: object on surface) exist, these scenarios primarily show balance rather than the dynamic interaction between two specific bodies causing relative motion, as typically highlighted for the third law.

• Option 4: A car accelerating involves action-reaction forces between the tires and the road. However, the interaction might be less intuitively clear compared to a direct push/pull between two distinct entities.

• Option 2: A sailor pushing the boat backward while jumping forward provides a direct and clear example:

  • Action: The sailor pushes backward on the boat. This force acts on the boat.
  • Reaction: The boat pushes forward on the sailor. This force acts on the sailor.

  These forces are equal in magnitude, opposite in direction, and act on two distinct objects (the sailor and the boat), perfectly matching the criteria of Newton's third law.

Conclusion

The situation involving the sailor and the boat explicitly demonstrates the action-reaction forces acting on two different objects, making it the clearest illustration of Newton's third law among the given options.