What completes the statement 'For every action, there is an equal and opposite ________'?

What completes the statement 'For every action, there is an equal and opposite ________'?

• A. Force
• B. Motion
• C. Reaction
• D. Energy

Answer: (C)

This is about Newton’s third law: for every action, there is an equal and opposite reaction. When one object pushes on another, the second object pushes back on the first with the same magnitude in the opposite direction. These two forces form an action–reaction pair and act on different objects at the same time. For example, pushing against a wall makes the wall push back on you with the same force in the opposite direction; a rocket ejecting exhaust backward causes the rocket to move forward. The completion is the word “reaction” because it denotes the counterforce on the other object in response to the action. The other options don’t fit because energy is not a force, motion is a result, and simply calling it a force wouldn’t capture the paired, opposite force acting on the other object.

This is about Newton’s third law: for every action, there is an equal and opposite reaction. When one object pushes on another, the second object pushes back on the first with the same magnitude in the opposite direction. These two forces form an action–reaction pair and act on different objects at the same time. For example, pushing against a wall makes the wall push back on you with the same force in the opposite direction; a rocket ejecting exhaust backward causes the rocket to move forward. The completion is the word “reaction” because it denotes the counterforce on the other object in response to the action. The other options don’t fit because energy is not a force, motion is a result, and simply calling it a force wouldn’t capture the paired, opposite force acting on the other object.