What is the difference between gravitational mass and inertial mass?

Gravitational mass is the property of an object that determines the force of gravity on it, while inertial mass is a measure of an object's resistance to changes in motion.

Gravitational mass is a measure of the amount of force with which an object is attracted towards other objects due to gravity. It is this property that gives weight to physical objects and causes them to fall towards the ground when dropped. The gravitational mass of an object can be determined using Newton's law of universal gravitation, which states that every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.

On the other hand, inertial mass is a measure of an object's resistance to acceleration when a net force is applied. It is a fundamental property of the object that determines how much it will accelerate under a given force according to Newton's second law of motion. The greater the inertial mass of an object, the less it accelerates under a given applied force.

Interestingly, in physics, the principle of equivalence states that gravitational and inertial mass are identical. This means that the force of gravity on an object (which depends on its gravitational mass) and the object's resistance to changing its state of motion (which depends on its inertial mass) are proportional. This principle is a cornerstone of Einstein's theory of general relativity.

In summary, while both gravitational and inertial mass are fundamental properties of matter, they describe different aspects of an object's interaction with forces: gravitational mass relates to the force of gravity acting on an object, while inertial mass relates to an object's resistance to changes in its state of motion.