4. physics

The length of the line segment formed between the start point and end point. In other words the distance from where you started to where you came from. If you went to California and back, the displacement is zero, even though the distance traveled would be, say, nearly 5000 miles if you lived in New York.

Denoted with the variable 'delta-x' (or delta-y or delta-z, depending on which dimension you are calculating).

There are two equations used to find displacement, or delta-x:

delta-x  =  (1/2)*(vi + vf)t

where t = time, vi = initial velocity, and vf = final velocity
(assuming acceleration is constant)


delta-x  =  vi  +  (1/2)* a * t2

where t = time, vi = initial velocity, and a = acceleration.

One of the ways of measuring the tonnage of a ship, essentially giving the entire volume of the vessel below the waterline, hence a figure equivalent to the mass of water displaced by the ship's own mass, hence again basically equal to the actual weight1 of the ship.

Displacement tonnage gives an measurement of the absolute size of a ship, without any reference to how the size and space are to be used; as such, it is mainly used for warships, including at various times in the past as a basis for limiting the size of ships under sundry naval treaties; for merchant shipping a variety of gross tonnage calculations of space usable for cargo are generally used instead. The most common displacement figures reported are of the vessel in an empty condition, light of fuel, munitions and other supplies that would always be carried in practice.

1. It is assumed here that we are only dealing with maritime activity on a single planet, since variations in gravity will generally lead to non-optimal performance, so weight=mass can be taken as read.

Dis*place"ment (?), n. [Cf. F. d'eplacement.]


The act of displacing, or the state of being displaced; a putting out of place.

Unnecessary displacement of funds. A. Hamilton.

The displacement of the sun by parallax. Whewell.


The quantity of anything, as water, displaced by a floating body, as by a ship, the weight of the displaced liquid being equal to that of the displacing body.

3. Chem.

The process of extracting soluble substances from organic material and the like, whereby a quantity of saturated solvent is displaced, or removed, for another quantity of the solvent.

Piston displacement Mech., the volume of the space swept through, or weight of steam, water, etc., displaced, in a given time, by the piston of a steam engine or pump.


© Webster 1913.

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