Liikumissuund

Liikumissuund is a term used in Estonian to describe the direction in which an object is moving at a given moment. It is a directional component of velocity, a vector quantity that combines speed (magnitude) and direction. The liikumissuund is often represented by a velocity vector v, where v = |v| u, with |v| the speed and u the unit vector indicating the direction of motion.

In two-dimensional coordinates, the direction can be described by an angle θ relative to a reference axis or by its components v_x and v_y. The instantaneous liikumissuund coincides with the tangent to the trajectory at that point; as the path (trajekt) changes, so can the direction.

In practical contexts such as navigation and traffic, liikumissuund indicates the intended or permissible direction of travel, for example the direction on a road or the bearing of a vessel. In biomechanics, it refers to the direction of a limb or body segment during movement.

Differences between related terms: liikumissuund is not the same as the path or trajekt. The path is the locus of points visited, while the liikumissuund is the direction along which motion occurs at each moment. The direction can change due to acceleration, curvature, or external forces.

Angles are often measured from a reference direction, such as true north, and can be computed using trigonometric relations. Examples include a car moving northeast, which has a liikumissuund of about 45 degrees from north, or a leaf drifting along a winding current where the liikumissuund changes over time.