Which law states that an object in motion stays in motion unless acted upon by an outside force?

Which law states that an object in motion stays in motion unless acted upon by an outside force?

• A. Newton's First Law
• B. Newton's Second Law
• C. Newton's Third Law
• D. Law of Gravity

Answer: (A)

Inertia is the tendency of an object to resist changes in its motion. An object that is moving will keep moving at the same speed and in the same direction unless a net external force acts on it to slow it down or change its path. On a frictionless surface, a puck would glide with constant velocity, illustrating this idea; in the real world, friction and air resistance slowly slow and stop moving objects, or a push and a collision can change their motion. This principle is Newton's First Law, often called the law of inertia. The other ideas describe different relationships: one links motion changes to the net force applied, showing how acceleration depends on force and mass; another describes interaction forces that occur in pairs; and the last explains how gravity attracts masses. The statement about motion persisting without external influence best matches Newton's First Law.

Inertia is the tendency of an object to resist changes in its motion. An object that is moving will keep moving at the same speed and in the same direction unless a net external force acts on it to slow it down or change its path. On a frictionless surface, a puck would glide with constant velocity, illustrating this idea; in the real world, friction and air resistance slowly slow and stop moving objects, or a push and a collision can change their motion. This principle is Newton's First Law, often called the law of inertia.

The other ideas describe different relationships: one links motion changes to the net force applied, showing how acceleration depends on force and mass; another describes interaction forces that occur in pairs; and the last explains how gravity attracts masses. The statement about motion persisting without external influence best matches Newton's First Law.