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Algebra of Vector Addition

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Estimated time: 10 minutes
CBSE: Class 12

Introduction

Vector addition explains how two or more vectors are combined to produce a single resultant vector. It is a fundamental concept in Vector Algebra and is also useful in physics applications such as displacement and velocity. Vector addition is introduced geometrically through the triangle law and parallelogram law.

CBSE: Class 12

Properties

Property Statement Meaning
Commutative Property \[(\vec{a}+\vec{b}=\vec{b}+\vec{a})\] Changing the order of vectors does not change the sum.
Associative Property \[((\vec{a}+\vec{b})+\vec{c}=\vec{a}+(\vec{b}+\vec{c}))\] Vectors can be grouped in any order while adding.
Additive Identity \[(\vec{a}+\vec{0}=\vec{0}+\vec{a}=\vec{a})\] The zero vector does not affect a vector when added.
Additive Inverse \[(\vec{a}+(-\vec{a})=\vec{0})\] Every vector has an opposite vector which gives the zero vector when added.
CBSE: Class 12

Triangle Law of Vector Addition

If two vectors are represented by two sides of a triangle taken in order, then their sum is represented by the third side of the triangle taken in the same order.

\[\vec{AB} + \vec{BC} = \vec{AC}\]
CBSE: Class 12

Parallelogram Law of Vector Addition

If two vectors are represented by two adjacent sides of a parallelogram, then their resultant is represented by the diagonal passing through their common initial point.

\[\vec{R} = \vec{a} + \vec{b}\]
CBSE: Class 12

Difference of Two Vectors

The difference of two vectors is obtained by adding the negative of one vector.

\[\vec{a} - \vec{b} = \vec{a} + (-\vec{b})\]
CBSE: Class 12

Real Life Examples

  • Walking path: A student walks 3 m east and then 4 m north; the direct displacement is the resultant vector.

  • Boat in a river: The motion of a boat crossing a river and the river current together form a resultant velocity, illustrating vector addition.

CBSE: Class 12

Key Points: Algebra of Vector Addition

  • A vector has both magnitude and direction.

  • Resultant means the combined effect of two or more vectors.

  • Triangle law uses head-to-tail arrangement.

  • Parallelogram law uses adjacent sides from the same initial point.

  • Vector addition is commutative and associative.

  • Zero vector is the identity element for vector addition.

  • Difference of vectors is obtained by adding the negative of a vector.

Shaalaa.com | Vector Algebra part 7 (Properties of Vector addition)

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