Which law states that an object at rest stays at rest and a moving object continues in its state of motion unless acted upon by a net external force?

• A. Newton's First Law of Motion
• B. Newton's Second Law of Motion
• C. Newton's Third Law of Motion
• D. Law of Conservation of Momentum

Answer: (A)

This statement is Newton's first law, often called the law of inertia. It says that in the absence of a net external force, an object will keep doing what it is already doing: if it’s at rest, it stays at rest; if it’s moving, it continues moving with the same speed and in the same direction. Inertia is the natural resistance of any object to changes in its motion. Forces like friction or air resistance are the net external influences that can change that state, causing a moving object to slow down or a resting object to start moving when a push is applied. This law sets the baseline for all motion, with the second and third laws and the momentum principle describing how and why motion changes when forces act, and how interactions balance out in a system.