Newton’s first law, also called the law of inertia, says that an object at rest will stay at rest or an object in motion will stay in motion unless acted upon by an external force. The second law states that force is equal to mass times acceleration (F=ma). This means that the more force is applied to an object, the more it will accelerate. The third law says that for every action, there is an equal and opposite reaction. This means that if you push on an object, the object pushes back with the same force in the opposite direction.