Which statement best describes Newton's second law?

Which statement best describes Newton's second law?

• A. An object's acceleration is proportional to the net force acting on it and in the direction of the force.
• B. An object at rest stays at rest unless acted upon by a net external force.
• C. For every action there is an equal and opposite reaction.
• D. Weight equals mass times gravity.

Answer: (A)

Newton's second law describes how an object's motion changes when a net external force acts on it: the acceleration is proportional to the net force and points in the same direction as that force. In other words, F_net = m a, so a = F_net / m. This means stronger forces produce more acceleration, and a lighter object accelerates more than a heavier one under the same force, with the direction of motion aligning with the force applied. The statement that matches this idea says acceleration is proportional to the net force and in the direction of the force. The other statements refer to different principles: inertia (an object at rest stays at rest unless a net external force acts), action-reaction pairs (Newton's third law), and weight as mass times gravity (a specific case on Earth, not the general description of how forces cause acceleration).

Newton's second law describes how an object's motion changes when a net external force acts on it: the acceleration is proportional to the net force and points in the same direction as that force. In other words, F_net = m a, so a = F_net / m. This means stronger forces produce more acceleration, and a lighter object accelerates more than a heavier one under the same force, with the direction of motion aligning with the force applied.

The statement that matches this idea says acceleration is proportional to the net force and in the direction of the force. The other statements refer to different principles: inertia (an object at rest stays at rest unless a net external force acts), action-reaction pairs (Newton's third law), and weight as mass times gravity (a specific case on Earth, not the general description of how forces cause acceleration).