Which statement correctly expresses Newton’s third law of motion?

• A. An object at rest stays at rest, and an object in motion stays in motion at constant velocity unless acted on by a net external force.
• B. When one object exerts a force on a second object, the second object exerts a force of equal magnitude and opposite direction on the first object.
• C. If the net force on an object is zero, the object must be at rest.
• D. The net force on an object equals its mass times its acceleration.

Answer: (B)

Verified step by step guidance

1. Identify that Newton's third law of motion deals with the interaction between two objects and the forces they exert on each other.
2. Recall the statement of Newton's third law: For every action, there is an equal and opposite reaction.
3. Understand that this means when one object applies a force on a second object, the second object simultaneously applies a force back on the first object with the same magnitude but in the opposite direction.
4. Compare this understanding with the given options to find the statement that matches this description exactly.
5. Confirm that the correct statement is: 'When one object exerts a force on a second object, the second object exerts a force of equal magnitude and opposite direction on the first object.'