Newton's Third Law Illustration

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that forces always occur in pairs. If object A exerts a force on object B, then object B simultaneously exerts a force on object A with the same magnitude but in the opposite direction.

Analyzing Motion Examples

Let's examine the options to see which best demonstrates this law:

• Option A: A ball falling under gravity. This primarily illustrates Newton's Second Law (acceleration due to net force) and the force of gravity. While the ball exerts an equal upward pull on the Earth, this effect is negligible and not the main focus.
• Option B: A rocket propelling upward by expelling gases downward. This is a direct application of Newton's Third Law. Action: The rocket exerts a downward force on the gases, expelling them. Reaction: The expelled gases exert an equal and opposite upward force on the rocket, propelling it.
• Option C: A car accelerating on a road due to engine power. While friction involves action-reaction forces (tire pushes road backward, road pushes tire forward), the primary phenomenon described is acceleration, governed mainly by Newton's Second Law.
• Option D: A pendulum oscillating back and forth. This demonstrates gravity, inertia, and periodic motion, not the action-reaction force pairs inherent in Newton's Third Law.

Conclusion

The rocket expelling gases is the clearest and most direct illustration of Newton's Third Law, showing a distinct action force (rocket pushing gas) and an equal, opposite reaction force (gas pushing rocket).