The natural tendency of an object to resist a change in its state of rest or motion.
Explanation
Inertia is a fundamental property of matter associated with Newton's First Law of Motion. It describes the inherent resistance of an object to any change in its state of motion, whether it is at rest or moving with a constant velocity.
Option Analysis
- The tendency of an object to accelerate under force. is incorrect: The tendency to accelerate under force is a response to an external influence, governed by Newton's Second Law ($F=ma$). Inertia is the property that opposes this acceleration.
- The natural tendency of an object to resist a change in its state of rest or motion. is correct: Inertia is defined as the natural tendency of an object to maintain its current state. If an object is at rest, it resists moving; if it is in motion, it resists stopping or changing direction, unless acted upon by an external unbalanced force.
- The force exerted by an object due to its mass. is incorrect: The force exerted by an object due to its mass under the influence of gravity is known as weight. Inertia is an intrinsic property, not a force.
- The momentum acquired by an object due to gravity. is incorrect: Momentum is the quantity of motion possessed by a moving body, calculated as the product of mass and velocity. While mass is a measure of inertia, momentum itself is a distinct vector quantity.
Key Takeaway
Inertia is the resistance of a body to changes in its state of rest or uniform motion. Mass is the quantitative measure of inertia; a heavier object possesses greater inertia.