In Newton's second law, which expression correctly relates force to mass and acceleration?

• A. Force equals mass times velocity
• B. Force equals velocity times acceleration
• C. Force equals mass times acceleration
• D. Force equals acceleration times velocity

Answer: (C)

Newton's second law states that the net force acting on an object equals its mass multiplied by its acceleration. Acceleration is the rate at which velocity changes, so force is what causes that change in motion. The expression that captures this relationship is force equals mass times acceleration. Its units are kilograms times meters per second squared, which are newtons. For example, a 5 kg object accelerated at 2 m/s^2 requires a 10 N force. Using velocity with force would tie force to how fast something is moving rather than how its motion changes, and momentum-related forms don’t describe the cause-and-effect relationship of force producing acceleration.