Final answer:
Newton's first law, known as the law of inertia, states that an object in motion or at rest will continue to be so unless acted upon by an external force. As this is a scientifically tested and accepted principle, it is classified as a law, not a theory or hypothesis. A law describes a single action, while a theory explains an entire group of related phenomena.
Step-by-step explanation:
The statement you are referring to is known as Newton's first law, also recognized as the law of inertia. This law presents that a body at rest remains at rest or, if moving, remains in motion at a constant speed in a straight line unless acted upon by an external force. Being that it's a proven and accepted principle in physics that explains a behavior pattern in nature, it is classified as a law, as per Option 2.
By definition, a scientific law is a concise statement that describes a generalized phenomena supported by scientific evidence and repeated experiments. Theories, in contrast, are more complex and explain an entire group of related phenomena. The biggest difference between a law and a theory is that a law describes a single consistent action, whereas a theory explains a broad grouping of interlinked actions.
To clarify further, the law of inertia (Newton's first law) states that objects will either remain in motion or stay at rest until an external force acts upon them. It is a fundamental concept in Newtonian physics and has been empirically tested and confirmed countless times. Therefore, it doesn't fit into the categories of a theory, which might require more supporting evidence, or a hypothesis, which necessitates further experimentation for its verification.
Learn more about Newton's first law