Gravitational Mass vs Inertial Mass
Gravitational mass and inertial mass are two widely debated and very useful concepts in physics. These two are defined using different approaches and require different measuring methods. These two concepts are extremely important in the field of classical mechanics. In this article, we are going to discuss what gravitational and mass inertial mass are, their definitions, the similarities between these two, their applications and finally the differences between the gravitational mass and the inertial mass.
What is Gravitational Mass?
A clear knowledge on the concept of gravity is required first, to understand the concept of gravitational mass. Gravity is the force that occurs due to any mass. Mass is the necessary and the sufficient condition for gravity. There is a gravitational field defined around any mass. Take masses m1 and m2 placed in a distance r from one another. The gravitational force between these two masses is G.m1.m2 / r2, where G is the universal gravitational constant. Since negative masses are not present, the gravitational force is always attractive. There are no repulsive gravitational forces. The gravitational mass is the mass defined by the above relationship. There are only two known ways to measure the gravitational mass of the earth. One is to apply Keplar’s law and calculate mass depending on the period. The second method is to find the acceleration of an object on the surface of the earth due to the gravity and use it to calculate the gravitational mass using the universal law of gravitation. It must be noted that even though the gravitational force depends on every particle of the mass, Gauss’ law states that only the mass enclosed by the closed surface will affect the gravitational force.
What is Inertial Mass?
First, it is essential to understand inertia and momentum, to understand the concept of inertial mass. The momentum of an object is equal to the mass of the object multiplied by the velocity of the object. Since the mass is a scalar, the momentum is a vector, which has the same direction as the velocity. One of the most fundamental laws regarding momentum is Newton’s second law of motion. It states that the net force acting on an object is equal to the rate of change of momentum. Inertia is the property of the object, which tries to retain the current system. The inertial mass is defined using Newton’s second law of motion. Since the inertial mass is constant, the second law takes the form of F = m a, where “F” is the net force acting on the object, “m” is the inertial mass of the object and “a” is the acceleration of the object. The inertial mass is defined as the net force, which is required to accelerate the object 1 meter per second per second.
What is the difference between Inertial Mass and Gravitational Mass?
• Gravitational mass is defined using the law of universal gravitation, while the inertial mass is defined using Newton’s second law of motion.
• However, both of these masses are equal in practice, and no difference between these two is found.