Liikemomentum

Liikemomentum is a term used to describe linear momentum, a fundamental quantity in classical mechanics that characterizes the motion of an object. It is defined as p = m v, where m is the object's mass and v is its velocity. Liikemomentum is a vector, pointing in the same direction as the velocity, and its SI unit is kilogram meter per second (kg·m/s). For a system of particles, the total liikemomentum is the vector sum of the momenta of all constituents.

In isolated or closed systems, liikemomentum is conserved: the total momentum remains constant over time when no external forces act on the system. This leads to the impulse-momentum theorem, Δp = ∫ F dt, where F is the external force applied over a time interval. During collisions or interactions, momentum can be redistributed among bodies, but the sum before and after remains the same.

Key properties include its role in describing motion independent of reference frame (to a degree explained by Galilean transformations in classical mechanics) and its relation to the motion of the system’s center of mass. The velocity of the center of mass V_cm equals the total momentum p_total divided by the total mass M.

Applications of liikemomentum span a wide range of problems, from analyzing collisions and projectile motion to understanding thrust and propulsion (where momentum is transferred to expelled mass). In relativistic contexts, momentum generalizes to p = γ m v, where γ is the Lorentz factor, and momentum is part of the four-momentum in special relativity.

See also: momentum, impulse, conservation laws, center of mass.