**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)*(v_{i} + v_{f})t

*where t = time, v*_{i} = initial velocity, and v_{f} = final velocity

(assuming acceleration is constant)
and

delta-x = v_{i} + (1/2)* a * t^{2}

*where t = time, v*_{i} = initial velocity, and a = acceleration.