NETA Personal Trainer Practice Exam

What does Newton's third law of action-reaction state regarding forces between two objects?

1. Forces are unopposed in an interaction

2. For every action, there is an equal and opposite reaction

3. Forces only occur in one direction

4. Acceleration is proportional to mass and force

The correct answer is: For every action, there is an equal and opposite reaction

Newton's third law of action-reaction articulates that when one object exerts a force on another object, the second object simultaneously exerts a force of equal magnitude but in the opposite direction back on the first object. This principle highlights the reciprocal nature of forces in interactions. In practical terms, this means that if you push against a wall, for instance, the wall pushes back against you with an equal force in the opposite direction. This law is fundamental for understanding interactions between objects, ensuring that the motion of one body influences another in a predictable way. The other options do not accurately describe this law. The first suggests that forces are unopposed, which contradicts the idea of equal and opposite forces. The third implies a unilateral directional nature of forces, failing to capture the mutual exertion of forces described by the law. The last relates to Newton’s second law regarding force, mass, and acceleration but does not pertain to the action-reaction principle.