Force equals mass multiplied by acceleration.

• A. Newton's Second Law
• B. Newton's First Law
• C. Newton's Third Law
• D. Law of Gravity

Answer: (A)

Force, mass, and acceleration are linked by a rule that says the net force on an object equals its mass times its acceleration. This is Newton's Second Law of Motion. It explains why heavier objects require a bigger push to reach the same acceleration, and why increasing acceleration for a given mass needs more force. For example, a 2-kilogram object accelerated at 3 meters per second squared requires a net force of 6 newtons. The other ideas describe different concepts: inertia, which is the tendency of moving objects to keep moving and of resting objects to stay at rest unless a net external force acts; action-reaction pairs, which are forces that occur in pairs during interactions; and gravity, which describes attraction between masses that depends on their masses and distance, not the direct F = m a relationship.