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summary of vector algebra

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Summary of Vector Algebra

Summary of vector algebra techniques in introductory physics:

Basic operations

−→
AB  =  rB − rA,

u + v =  v + u,     (u + v) + w =  u + (v + w ),

u −  v = u + (− v),

a (u +  v) = au + av,     (a + b)u = au  + bu.

Linear and affine representations

If a,b are nonparallel, every vector in their plane is αa + βb. If a,b,c are noncoplanar, every vector in space is

αa + βb +  γc.

For point division,

rP =  nrA-+-mrB--.
        m +  n

For weighted points,

      ∑
rG  = -∑-imiri.
         imi

Cartesian components

      ˆ     ˆ     ˆ          2    2    2    2
u = ux i + uyj + uzk,    ∥u ∥ =  ux + uy + uz.

Dot product

u ⋅ v = ∥u ∥∥v∥ cos𝜃 = uxvx + uyvy + uzvz.

For nonzero vectors,

u ⋅ v = 0 ⇐⇒   u ⊥  v.

Cross product

u × v =  ∥u∥∥v ∥ sin 𝜃 ˆn,

u ×  v = − v × u,

        |           |
        || ˆi   ˆj   ˆk ||
u × v = |ux  uy  uz |.
        ||v   v    v ||
          x    y   z

For nonzero vectors,

u ×  v = 0  ⇐⇒   u ∥ v.

Triple products

(u × v ) ⋅ w = det[u v w ],

whose absolute value is the parallelepiped volume, and

u × (v ×  w) = v (u ⋅ w ) − w (u ⋅ v).

These identities form the working vector toolkit used throughout the remainder of Vectorial mechanics.

Modern notation references

The notation and terminology in this modernized article follow standard present-day mechanics and vector-analysis usage, particularly:

  1. J. R. Taylor, Classical Mechanics, University Science Books, 2005.
  2. D. Kleppner and R. Kolenkow, An Introduction to Mechanics, 2nd ed., Cambridge University Press, 2014.
  3. H. Goldstein, C. Poole, and J. Safko, Classical Mechanics, 3rd ed., Addison–Wesley, 2002.

Source

This article is a modernized restatement of the corresponding Public article in Louis Brand, Vectorial Mechanics, John Wiley & Sons, New York, 1930, Chapter I, “Vector Algebra.” The original 1930 edition is the source basis.


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See Also: dot product algebra and geometric applications, dot product, vector product, centroids and weighted position vectors, Cartesian components and direction cosines, scalar component and vector projection on an Axis, vectors in space, vectors in a plane, vector subtraction and position vectors, negative of a vector, equality of vectors, vector, vector algebra, vector addition, point division and position vectors, cross product, cross product algebra and applications, scalar triple product


Cross-references: mechanics, volume, vector

This is version 2 of summary of vector algebra, born on 2026-08-22, modified 2026-08-22.
Object id is 1083, canonical name is SummaryOfVectorAlgebra.
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Classification:
Physics Classification: 02. (Mathematical methods in physics)

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