The Collaborative International Dictionary
Velocity \Ve*loc"i*ty\, n.; pl. Velocities. [L. velocitas, from velox, -ocis, swift, quick; perhaps akin to v?lare to fly (see Volatile): cf. F. v['e]locit['e].]
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Quickness of motion; swiftness; speed; celerity; rapidity; as, the velocity of wind; the velocity of a planet or comet in its orbit or course; the velocity of a cannon ball; the velocity of light.
Note: In such phrases, velocity is more generally used than celerity. We apply celerity to animals; as, a horse or an ostrich runs with celerity; but bodies moving in the air or in ethereal space move with greater or less velocity, not celerity. This usage is arbitrary, and perhaps not universal.
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(Mech.) Rate of motion; the relation of motion to time, measured by the number of units of space passed over by a moving body or point in a unit of time, usually the number of feet passed over in a second. See the Note under Speed.
Angular velocity. See under Angular.
Initial velocity, the velocity of a moving body at starting; especially, the velocity of a projectile as it leaves the mouth of a firearm from which it is discharged.
Relative velocity, the velocity with which a body approaches or recedes from another body, whether both are moving or only one.
Uniform velocity, velocity in which the same number of units of space are described in each successive unit of time.
Variable velocity, velocity in which the space described varies from instant, either increasing or decreasing; -- in the former case called accelerated velocity, in the latter, retarded velocity; the acceleration or retardation itself being also either uniform or variable.
Virtual velocity. See under Virtual.
Note: In variable velocity, the velocity, strictly, at any given instant, is the rate of motion at that instant, and is expressed by the units of space, which, if the velocity at that instant were continued uniform during a unit of time, would be described in the unit of time; thus, the velocity of a falling body at a given instant is the number of feet which, if the motion which the body has at that instant were continued uniformly for one second, it would pass through in the second. The scientific sense of velocity differs from the popular sense in being applied to all rates of motion, however slow, while the latter implies more or less rapidity or quickness of motion.
Syn: Swiftness; celerity; rapidity; fleetness; speed.
Wikipedia
The relative velocity v⃗ (also v⃗ or v⃗) is the velocity of an object or observer B in the rest frame of another object or observer A.
Usage examples of "relative velocity".
Even a conventionally armed fleet, with old-style compensators, and a relative velocity on translation of zero, could have achieved a zero/zero intercept with the planet in under an hour.
But their relative velocity was losing ground steadily, anyway, and the turn also brought all of their broadside fire control to bear.
Not because I wanted to punish the same people who massacred my people at Hyacinth, but because I wanted-needed-to take them out, whoever they were, so fast and so hard, from such a close range and at such a low relative velocity, that they wouldn't even dream of dumping their computer cores when I told them not to.
Until her own sensors picked up Danislav's ships she could only decelerate back the way she'd come, and every second of deceleration increased Nike's relative velocity by nine KPS.
Data began to pour in: distance, size, composition, relative velocity from half a hundred obstacles at once.
If we go for a least-time flight from that point, we can reach the planet in another hundred and seventeen minutes, call it three hours and twenty minutes total, but our relative velocity would be over thirty-six thousand KPS.
The destroyer was a full thirty light-seconds astern now, with a relative velocity of over thirty thousand KPS, and she was already deploying missile decoys.
A dozen monitors displayed magnetic fluctuations, relative velocity, comet brightness, spectrum analysis.
Their point defense should have taken toll of these fighters that so unexpectedly swept past them at an unthinkable relative velocity, clawing their ship's flanks with lasers.
Then the two forces interpenetrated at an unthinkable relative velocity, and that instant of interpenetration was marked by a brief but searingly intense exchange of energy weapon fire in which a hundred and twenty gunboats died.
The tracker just showed relative velocity, not which object was doing the moving.
I doubt that any of them could survive impact at what the relative velocity was at the time, but….
I doubt that any of them could survive impact at what the relative velocity was at the time, but.