Nurkjõudlust

Nurkjõudlust, often translated as rotational inertia or moment of inertia, is a fundamental concept in physics describing an object's resistance to changes in its rotational motion. It is the rotational analog of mass, which measures resistance to changes in linear motion. Just as a larger mass requires more force to accelerate linearly, a larger nurkjõudlust requires more torque to accelerate rotationally.

The nurkjõudlust of an object depends not only on its mass but also on how that mass is distributed relative to the axis of rotation. Mass concentrated further from the axis contributes more to the nurkjõudlust than mass located closer to the axis. This is why a figure skater can spin faster by pulling their arms in; their nurkjõudlust decreases, allowing for a greater angular velocity given the same angular momentum.

Mathematically, nurkjõudlust is calculated by summing the product of each infinitesimal mass element and the square of its perpendicular distance from the axis of rotation. For a collection of point masses, it is the sum of the mass of each particle multiplied by the square of its distance from the axis. For continuous bodies, this becomes an integral. The unit of nurkjõudlust in the International System of Units is kilogram-meter squared (kg⋅m²). Understanding nurkjõudlust is crucial for analyzing the motion of rotating systems, from planets to machinery.