^^Grandezze scalari e vettoriali.

• grandezza scalare
  • grandezza scalare assoluta, cioe' senza segno
  • grandezza scalare relativa, cioe' con segno
• grandezza vettoriale

Approfondimento

Scalars and Vectors.

From: The dynamics of particles and of rigid, elastic, and fluid bodies. Being lectures on mathematical physics (1912) Webster, Arthur Gordon, 1863-1923

In mathematics we have to consider two sorts of quantities,

• those which do not involve the idea of direction, called by Hamilton scalars (because they may be specified by numbers marked off on a scale),
• and those which do, called steps or vectors.

The distance between two points  x₁, y₁, z₁,  x₂, y₂, z₂
s = √ (  (x₂ - x₁)² + (y₂ - y₁)² + (z₂ - z₁)²  )
is a scalar, whereas the geometrical difference in position of the two points is known only when we specify not merely the length, but also the direction of the line joining them.