What is described by Newton's Third Law of Motion?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This principle emphasizes the intrinsic relationship between forces. When one object exerts a force on a second object, the second object simultaneously exerts a force of equal magnitude but in the opposite direction back on the first object. This means that forces occur in pairs, showcasing the interaction between two bodies.

For example, when you push against a wall, your hand applies a force on the wall, and the wall pushes back with a force of equal intensity in the opposite direction. This law is fundamental in understanding motion and interactions between objects, highlighting that forces are not isolated but are part of a reciprocal interaction.

The other options do not accurately reflect this fundamental principle. Forces do not exist independently because they are always associated with interactions between objects. While it is true that an object can remain in motion without the presence of a net external force (as stated in Newton’s First Law), this does not relate directly to the concept of action and reaction. Lastly, the idea that every motion has a corresponding motion in the same direction does not capture the essence of force interactions, as it doesn't account for the opposite nature of the reaction forces described in Newton's Third Law.