MOI of Hollow Sphere Full Handwritten Notes Of B.Sc  Physics



The moment of inertia is a physical property that quantifies an object's resistance to rotational motion. When considering a hollow sphere, which is a three-dimensional object with a spherical shape and empty interior, determining its moment of inertia becomes crucial.


To calculate the moment of inertia of a hollow sphere, we need to examine its geometry and distribution of mass. A hollow sphere consists of an outer radius (R) and an inner radius (r), with R being larger than r. The difference between the outer and inner radii creates a thin spherical shell.


Deriving the moment of inertia for a hollow sphere involves integrating infinitesimally small mass elements throughout its volume. Each element contributes to the overall rotational inertia. The integral takes into account the radial distance from the sphere's axis of rotation, as well as the mass distribution within the spherical shell.


The formula for calculating the moment of inertia (I) of a hollow sphere is I = (2/3) * m * (R^2 + r^2), where m represents the mass of the hollow sphere. This equation demonstrates that the moment of inertia of a hollow sphere is proportional to the sum of the squares of the outer and inner radii.


To illustrate this concept, let's consider an example. Suppose we have a hollow sphere with an outer radius of 10 cm and an inner radius of 8 cm. If the mass of the sphere is 2 kg, we can use the formula to calculate its moment of inertia:


I = (2/3) * 2 kg * [(0.1 m)^2 + (0.08 m)^2] = 0.048 kg.m^2


Hence, the moment of inertia for this particular hollow sphere is 0.048 kg.m^2.


In conclusion, understanding the moment of inertia of a hollow sphere requires considering its geometry and mass distribution. By employing relevant formulas, we can accurately calculate the rotational inertia possessed by a hollow sphere, providing valuable insights into its rotational behavior.


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