Pyörimismäärän

Pyörimismäärän, also known as angular momentum, is a fundamental concept in physics that describes the rotational inertia of an object. It is the rotational analogue of linear momentum and is a conserved quantity in a closed system, meaning it remains constant unless acted upon by an external torque.

The magnitude of pyörimismäärän for a point mass is given by the product of its mass, velocity, and the perpendicular distance from the axis of rotation. For a rigid body, pyörimismäärän is calculated by summing the pyörimismäärän of all its constituent particles, taking into account their distribution around the axis of rotation. This is often expressed as the product of the body's moment of inertia and its angular velocity. The moment of inertia quantifies how resistant an object is to changes in its rotational motion, similar to how mass resists changes in linear motion.

Pyörimismäärän is a vector quantity, meaning it has both magnitude and direction. Its direction is typically defined by the right-hand rule, pointing along the axis of rotation. This conserved quantity plays a crucial role in understanding the motion of planets, gyroscopes, and subatomic particles. For instance, the conservation of pyörimismäärän explains why an ice skater spins faster when they pull their arms in. Similarly, it is fundamental to the stability of rotating systems and the description of quantum mechanical states.