Which principle states that an object's inertia is dependent on its mass?

The correct response highlights Newton's first law, often referred to as the law of inertia. This principle asserts that an object will maintain its state of rest or uniform motion unless acted upon by an external force. It establishes a direct relationship between an object's mass and its inertia, meaning that the greater the mass of an object, the greater its resistance to changes in its motion. Essentially, inertia is a property of matter that quantifies how much an object resists acceleration when a force is applied, and this resistance increases with mass.

In contrast, the other principles revolve around different concepts. Newton's second law articulates the relationship between force, mass, and acceleration (F=ma), which while related to the inertia of an object, does not primarily define it. Newton's third law emphasizes the concept of action and reaction forces, stating that for every action there is an equal and opposite reaction, but it does not directly address inertia itself. Finally, the principle of conservation of energy deals with the transformation of energy in interactions and is not related to inertia or mass in the context of motion.