Which option shows a correct Newton's Third Law example?

Which option shows a correct Newton's Third Law example?

• A. A ball rolling on a track slows down due to friction
• B. An inflated balloon moves through the air when a jet of air leaves its neck as it deflates
• C. A book resting on a table
• D. A person jumping off a boat

Answer: (B)

Newton's Third Law says forces come in equal and opposite pairs acting on two interacting objects. In this balloon example, air is expelled through the neck as the balloon deflates. The balloon pushes on the air to drive it outward, and the air pushes back on the balloon with the same force in the opposite direction. That reaction force propels the balloon forward. It’s the clearest illustration because the forces clearly occur on two separate objects and produce observable motion: the balloon moves forward while the air moves backward. Other scenarios involve forces in ways that aren’t as direct demonstrations of two-object action–reaction pairs driving motion, even though those forces exist in different contexts.

Newton's Third Law says forces come in equal and opposite pairs acting on two interacting objects. In this balloon example, air is expelled through the neck as the balloon deflates. The balloon pushes on the air to drive it outward, and the air pushes back on the balloon with the same force in the opposite direction. That reaction force propels the balloon forward. It’s the clearest illustration because the forces clearly occur on two separate objects and produce observable motion: the balloon moves forward while the air moves backward.

Other scenarios involve forces in ways that aren’t as direct demonstrations of two-object action–reaction pairs driving motion, even though those forces exist in different contexts.