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Grade 12th passMechanics

Ratio if gravitational mass to inertial massHow to justify that it`s answer is 1 ???

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8 Years agoGrade 12th pass
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ApprovedApproved Tutor Answer1 Year ago

To understand why the ratio of gravitational mass to inertial mass is equal to 1, we need to delve into the definitions of these two types of mass and how they interact in the context of physics. Let’s break this down step by step.

Defining Gravitational and Inertial Mass

Gravitational mass refers to the property of an object that determines the strength of the gravitational force it experiences in a gravitational field. Essentially, it tells us how much an object will be attracted to another object due to gravity. On the other hand, inertial mass is a measure of an object's resistance to acceleration when a force is applied. In simpler terms, it indicates how much force is needed to change the object's state of motion.

The Equivalence Principle

The key concept that connects these two types of mass is known as the equivalence principle, which is a cornerstone of Einstein's theory of general relativity. This principle states that gravitational mass and inertial mass are equivalent; that is, they are the same quantity. This equivalence can be observed in various experiments and is fundamental to our understanding of gravity.

Mathematical Justification

Let’s look at the mathematical aspect to clarify why the ratio is 1. The gravitational force acting on an object can be expressed using Newton's law of gravitation:

  • F_gravity = G * (m1 * m2) / r²

Here, F_gravity is the gravitational force, G is the gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between their centers. If we consider one of these masses to be the gravitational mass (m_g), we can rewrite the equation as:

  • F_gravity = G * (m_g * M) / r²

Now, according to Newton's second law, the force acting on an object is also equal to the product of its inertial mass (m_i) and its acceleration (a):

  • F = m_i * a

When an object is in free fall, the only force acting on it is gravity, so we can set these two expressions for force equal to each other:

  • m_i * a = G * (m_g * M) / r²

In free fall, the acceleration (a) is equal to the gravitational acceleration (g), which leads us to:

  • m_i * g = G * (m_g * M) / r²

From this equation, if we rearrange it, we can see that:

  • m_i / m_g = G * M / (r² * g)

In a uniform gravitational field, this ratio simplifies to 1, demonstrating that:

  • m_i = m_g

Experimental Evidence

Numerous experiments have been conducted to test the equivalence of gravitational and inertial mass. For instance, the famous Eötvös experiment and others have shown that the ratio remains consistent across different materials and conditions, reinforcing the idea that both types of mass are indeed equivalent.

Implications in Physics

This equivalence has profound implications in physics, particularly in the formulation of general relativity, where gravity is not viewed as a force but rather as a curvature of spacetime caused by mass. The fact that gravitational and inertial mass are the same allows us to describe the motion of objects under gravity in a unified way.

In summary, the ratio of gravitational mass to inertial mass is justified as being equal to 1 based on both theoretical foundations and experimental evidence, illustrating a fundamental aspect of how mass interacts with forces in our universe.