Rotational Dynamics

torque due to couple

Torque in rotational motion

We know about the definition of force in linear motion as an external agent to change the state of rest or of uniform motion in a straight line according to Newton’s first law of motion. Similarly, the rotating force is required to change the state of rest or of uniform motion in a circular motion and that rotating force is called torque.

moment of inertia of rod about center

Calculation of Moment of Inertia in different bodies

1] Moment of Inertia of the thin rod about an axis perpendicular to its plane and passing through a center. Let us consider a thin uniform rod of mass ‘M’ and length ‘L’ rotating about a perpendicular axis and passing through a center. Consider a small element of thickness ‘dx’ of mass ‘dm’ at a …

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theorem on perpendicular axis

Theorem on the Moment of Inertia

There are two theorems on a moment of inertia that helps to calculate the moment of inertia of any rigid body. They are:
This theorem states that the moment of inertia of a plane lamina about a perpendicular axis to the plane lamina is equal to the sum of the moment of inertia of plane lamina under two axes on a plane right angle to each other and intersecting at a point through which a perpendicular axis passes.