What is the second law of motion?

• A. Velocity
• B. Acceleration
• C. Force
• D. Momentum

Answer: (B)

Newton's second law states that motion changes when a net external force acts on a mass, linking force, mass, and acceleration. If a net force F acts on a body of mass m, it accelerates with a = F/m, and the acceleration points in the direction of the force. In other words, force causes acceleration, and the size of that acceleration grows with the force and shrinks with greater mass.

Among the options, acceleration best represents what this law describes because it is the result of applying force to a mass. Velocity describes how fast something is moving at an instant and doesn’t capture the cause‑and‑effect relation. Momentum is mass times velocity and is related to motion but isn’t the law itself. Force is the cause in the relation, but the second law is about how that force translates into acceleration.