In Newton's laws of motion, how is action related to reaction?

• A. Action and reaction occur at different times.
• B. For every action there is an equal or opposite reaction.
• C. Action is greater than the reaction.
• D. Reaction occurs only after a threshold force.

Answer: (B)

Newton's third law states that forces come in action–reaction pairs: for every force there is an equal in magnitude and opposite in direction force that arises from the interaction between two objects. These two forces act on different bodies and are effectively simultaneous, so they don’t cancel each other out. For example, pushing on a wall makes the wall push back with the same strength in the opposite direction, and a rocket is propelled forward as the expelled gas pushes backward.