Which statement describes Newton's third law of motion?

Which statement describes Newton's third law of motion?

• A. Every action has an equal and opposite reaction
• B. Force is equal to mass x acceleration
• C. An object will not change its motion unless a force acts upon it
• D. Energy cannot be created nor destroyed

Answer: (A)

Forces come in action–reaction pairs: the push from one object on another has a counterpart that is equal in magnitude but opposite in direction, and it acts on the other object. These forces occur simultaneously and act on different bodies, which is why they don’t cancel each other out in the system’s motion. That description matches Newton's third law. Think of pushing against a wall—the wall pushes back with the same force you push on it. Or a rocket thrusting exhaust gas backward to propel the rocket forward. In each case, the two forces are equal and opposite, acting on two separate objects. Other statements describe different ideas: one is about how acceleration relates to force (F = m a), another is about an object's tendency to keep moving unless a force acts (inertia), and another is about energy not being created or destroyed. These aren’t the third-law pair, but they help distinguish the distinct laws of motion and energy.

Forces come in action–reaction pairs: the push from one object on another has a counterpart that is equal in magnitude but opposite in direction, and it acts on the other object. These forces occur simultaneously and act on different bodies, which is why they don’t cancel each other out in the system’s motion.

That description matches Newton's third law. Think of pushing against a wall—the wall pushes back with the same force you push on it. Or a rocket thrusting exhaust gas backward to propel the rocket forward. In each case, the two forces are equal and opposite, acting on two separate objects.

Other statements describe different ideas: one is about how acceleration relates to force (F = m a), another is about an object's tendency to keep moving unless a force acts (inertia), and another is about energy not being created or destroyed. These aren’t the third-law pair, but they help distinguish the distinct laws of motion and energy.