Learn English – Word for change in velocity

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Is there a good word for change in velocity, but not over time? That is, position is to displacement as velocity is to what?

Best Answer

The standard term for a difference of velocities is delta-v.

Quoting Wikipedia (I know, I know!):

In general physics, delta-v is simply the change in velocity. The Greek letter delta is a standard mathematical symbol to represent change (and can be thought of as a fulcrum with a beginning and ending state).
Depending on the situation, delta-v can be referred to as a spatial vector (Δv) or scalar (Δv). In both cases it is equal to the acceleration (vector or scalar) integrated over time:

(Sadly, I don't know enough TeX to include the equations here.)

The term "delta-V" has another, closely-related meaning that brings back a good deal of nostalgia, in this week of watching the Endeavour fly to its final home:

In astrodynamics a Δv or delta-v (literally "change in velocity") is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver.
Delta-v is produced by the use of propellant by reaction engines to produce a thrust that accelerates the vehicle.

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