velocitychanges

Velocity changes describe the alteration of an object's velocity between two points in time. Formally, if an object has velocity v1 at time t1 and velocity v2 at time t2, the velocity change is Δv = v2 − v1. Because velocity is a vector, Δv includes changes in both speed and direction; its magnitude |Δv| quantifies the total change in velocity, while the direction of Δv indicates how the velocity vector has rotated or reoriented.

Acceleration is the time derivative of velocity, and the average acceleration over the interval is Δv/Δt. The instantaneous acceleration is the limit as Δt approaches zero. Impulse equals the change in momentum, J = Δp = m Δv, where m is the object's mass.

In practical terms, velocity changes occur whenever a force acts on an object. Examples include a car turning a corner (velocity changes direction), braking (speed decreases), or a rocket engine performing a delta-v maneuver to adjust speed and trajectory. In orbital mechanics and aerospace, the term delta-v is widely used to denote the total velocity change required for a maneuver.

Measuring velocity changes involves sensors such as radar, lidar, or inertial measurement units in vehicles and spacecraft. When reporting velocity changes, it is important to specify the time interval and frame of reference, since different frames can yield different Δv.

See also: acceleration, velocity, momentum, impulse, delta-v.