Which law relates the acceleration of an object to the net force acting on it and its mass?

Which law relates the acceleration of an object to the net force acting on it and its mass?

• A. Newton's Second Law of Motion
• B. Newton's Third Law of Motion
• C. The Law of Inertia
• D. Law of Universal Gravitation

Answer: (A)

The key idea here is how a net external force causes an object to accelerate, and how that acceleration depends on the object's mass. This is captured by Newton's Second Law of Motion, commonly written as F_net = m a. It tells us that acceleration is directly proportional to the net force and inversely proportional to the mass. So, doubling the net force on the same object doubles its acceleration, while doubling the mass with the same net force halves the acceleration. The direction of the acceleration follows the direction of the net force. This distinguishes it from the other ideas: the law about action and reaction pairs describes forces that come in pairs acting on different objects; the law about inertia states that an object at rest stays at rest and an object in motion stays in motion unless a net external force acts; and the law of universal gravitation explains the gravitational attraction between masses. None of these alone express the direct relationship between net force, mass, and acceleration in the way F_net = m a does.

The key idea here is how a net external force causes an object to accelerate, and how that acceleration depends on the object's mass. This is captured by Newton's Second Law of Motion, commonly written as F_net = m a. It tells us that acceleration is directly proportional to the net force and inversely proportional to the mass. So, doubling the net force on the same object doubles its acceleration, while doubling the mass with the same net force halves the acceleration. The direction of the acceleration follows the direction of the net force.

This distinguishes it from the other ideas: the law about action and reaction pairs describes forces that come in pairs acting on different objects; the law about inertia states that an object at rest stays at rest and an object in motion stays in motion unless a net external force acts; and the law of universal gravitation explains the gravitational attraction between masses. None of these alone express the direct relationship between net force, mass, and acceleration in the way F_net = m a does.