What does F = ma describe?

• A. Law of conservation of energy
• B. The relationship between mass, acceleration, and applied force
• C. Action-reaction pairs
• D. Equilibrium of forces

Answer: (B)

Newton's second law describes how motion responds to force: the net force acting on an object equals its mass times the acceleration it experiences. The acceleration points in the same direction as the net force, and its magnitude scales with both the net force and the object's mass—doubling the net force doubles the acceleration, while doubling the mass for the same force halves the acceleration. If no net force acts, the acceleration is zero, so the object moves with constant velocity or stays at rest. The equation also tells us the units: force is measured in newtons, which are kilograms meters per second squared. This relationship illustrates how mass, force, and motion are linked, and it’s distinct from energy conservation, action–reaction pairs, or equilibrium, which describes a balance of forces with zero net force.