Vector

8.1 Vector
 
An informative mind map that contrasts scalar and vector quantities, showcasing vector for clarity.
 
Example
Scalar Quantity Vector Quantity
Distance Displacement
Speed Velocity
Mass Weight
 
Vector
Figure

Visualization of vector 'a' on a line with initial and terminal points, from point A to B.

Characteristics
  • A vector is usually represented by a directed line segment drawn as an arrow.
  • The length of the line represents the magnitude or the size of the vector and the arrow indicates the direction of the vector.
  • A vector from an initial point \(A\) to a terminal point \(B\) can be written as \(\overrightarrow{AB}\)\(\utilde{a}\)\(AB\) or \(a\).
  • Vector \(-\overrightarrow{AB}\) represents a vector in the opposite direction as that is \(\overrightarrow{AB}\), such that \(\overrightarrow{BA}=-\overrightarrow{AB}\).
  • Two vectors are equal if and only if both the vectors have the same magnitude and direction.
  • A zero vector \(\utilde{0}\) has magnitude zero and its direction cannot be determined.

  • The vector \(\utilde{a}\) multiplied by the scalar \(k\) is also a vector and is written as \(k\utilde{a}\) where

    (i) \( \begin{vmatrix} ka \end{vmatrix}=k \begin{vmatrix} ka \end{vmatrix}\).

    (ii) if \(k \gt0\), then \(k\utilde{a}\) has the same direction as \(\utilde{a}\).

    (iii) if \(k \lt0\), then \(k\utilde{a}\) has the opposite direction as \(\utilde{a}\).

  • Vector \(\utilde{a}\) and \(\utilde{b}\) are parallel if and only if \(\utilde{a}=k\utilde{a}\) where \(k\) is a constant.

 
Example \(1\)
Question

Given the vector \(\utilde{m}\).

Blue background with a line representing vector 'm'.

Express the vector below in term of \(\utilde{m}\).

Line graph showing vector with red line fluctuating up and down.
Solution

Based on the given diagram,

the vector has twice the magnitude of the vector \(\utilde{m}\) and also due in same direction with vector \(\utilde{m}\).


Hence, the vector in term of \(\utilde{m}\) is:

\(2\utilde{m}\).

 
Example \(2\)
Question

Given a pair of vector.

Determine whether the pair of vector is parallel or not.

\(\overrightarrow{EF}=\dfrac{1}{3}\utilde{r}\)

\(\overrightarrow{FG}=9\utilde{r}\)

Solution

Vector \(\utilde{a}\) and \(\utilde{b}\) are parallel if and only if \(\utilde{a}=k\utilde{b}\) where \(k\) is a constant.

\(\overrightarrow{EF}=\dfrac{1}{3}\utilde{r}\),

Then,

\(\utilde{r}=3\overrightarrow{EF}\).


Hence,

\(\begin{aligned} \overrightarrow{FG}&=9(3\overrightarrow{EF})\\\\ &=27\overrightarrow{EF}. \end{aligned}\)

\(\therefore \overrightarrow{EF}\) and \(\overrightarrow{FG}\) are parallel.

 

Vector

8.1 Vector
 
An informative mind map that contrasts scalar and vector quantities, showcasing vector for clarity.
 
Example
Scalar Quantity Vector Quantity
Distance Displacement
Speed Velocity
Mass Weight
 
Vector
Figure

Visualization of vector 'a' on a line with initial and terminal points, from point A to B.

Characteristics
  • A vector is usually represented by a directed line segment drawn as an arrow.
  • The length of the line represents the magnitude or the size of the vector and the arrow indicates the direction of the vector.
  • A vector from an initial point \(A\) to a terminal point \(B\) can be written as \(\overrightarrow{AB}\)\(\utilde{a}\)\(AB\) or \(a\).
  • Vector \(-\overrightarrow{AB}\) represents a vector in the opposite direction as that is \(\overrightarrow{AB}\), such that \(\overrightarrow{BA}=-\overrightarrow{AB}\).
  • Two vectors are equal if and only if both the vectors have the same magnitude and direction.
  • A zero vector \(\utilde{0}\) has magnitude zero and its direction cannot be determined.

  • The vector \(\utilde{a}\) multiplied by the scalar \(k\) is also a vector and is written as \(k\utilde{a}\) where

    (i) \( \begin{vmatrix} ka \end{vmatrix}=k \begin{vmatrix} ka \end{vmatrix}\).

    (ii) if \(k \gt0\), then \(k\utilde{a}\) has the same direction as \(\utilde{a}\).

    (iii) if \(k \lt0\), then \(k\utilde{a}\) has the opposite direction as \(\utilde{a}\).

  • Vector \(\utilde{a}\) and \(\utilde{b}\) are parallel if and only if \(\utilde{a}=k\utilde{a}\) where \(k\) is a constant.

 
Example \(1\)
Question

Given the vector \(\utilde{m}\).

Blue background with a line representing vector 'm'.

Express the vector below in term of \(\utilde{m}\).

Line graph showing vector with red line fluctuating up and down.
Solution

Based on the given diagram,

the vector has twice the magnitude of the vector \(\utilde{m}\) and also due in same direction with vector \(\utilde{m}\).


Hence, the vector in term of \(\utilde{m}\) is:

\(2\utilde{m}\).

 
Example \(2\)
Question

Given a pair of vector.

Determine whether the pair of vector is parallel or not.

\(\overrightarrow{EF}=\dfrac{1}{3}\utilde{r}\)

\(\overrightarrow{FG}=9\utilde{r}\)

Solution

Vector \(\utilde{a}\) and \(\utilde{b}\) are parallel if and only if \(\utilde{a}=k\utilde{b}\) where \(k\) is a constant.

\(\overrightarrow{EF}=\dfrac{1}{3}\utilde{r}\),

Then,

\(\utilde{r}=3\overrightarrow{EF}\).


Hence,

\(\begin{aligned} \overrightarrow{FG}&=9(3\overrightarrow{EF})\\\\ &=27\overrightarrow{EF}. \end{aligned}\)

\(\therefore \overrightarrow{EF}\) and \(\overrightarrow{FG}\) are parallel.