5.1.2
Vectors 2
Scalars and Straight Lines
Scalars and Straight Lines
A scalar is any number such as 10, π, -4, 1⁄2, 4.52, √6.


Scalars and vectors
Scalars and vectors
- When a vector is multiplied by a scalar its direction does not change but its size does.
- A negative scalar switches the direction of the vector.
- To multiply a column vector by a scalar multiply both top and bottom numbers by the scalar.


Straight lines
Straight lines
- To show 3 points A, B and C lie in a straight line show that AB is a scalar multiple of BC.


Ratios and lengths
Ratios and lengths
- If given side lengths in ratios you can translate this to vector form.
- If AB : BC = 2 : 3 and A, B, C are in a straight line then 2 AB = 3 BC.
Magnitude of Vectors
Magnitude of Vectors
Vectors have a magnitude (size) and direction. The magnitude of a vector can be calculated from the column vector.
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Calculating the magnitude
Calculating the magnitude
- You can use Pythagoras' theorem to calculate the magnitude of a vector ().
- The magnitude of a vector is .


Vector notation
Vector notation
- You will need to be careful when writing vectors in your exam.
- Vectors will be printed on the exam as or a.
- The magnitude of a vector will be shown using modulus signs.
- I.e. magnitude of = ||
- I.e. magnitude of a = |a|


Using vector notation
Using vector notation
- In your exam, you will need to show the examiner that you know the difference between the vector a and the letter a.
- There are two ways to do this:
- Using an arrow above the vector, e.g.
- Underlining the letter, e.g.
Proof by Vector Method
Proof by Vector Method
Vectors can be used to prove geometric properties of shapes.


Example
Example
- By method of vectors, prove that STU is a straight line.


Draw the diagram
Draw the diagram
- Remember to label each points carefully.


Work out the vectors
Work out the vectors
- Work out the vectors for the points connecting the path from S to T to U, in terms of the vectors p and q.


Compare
Compare
- Compare the vector ST with the vector TU.
- If STU is a straight line, then ST and TU will be multiples of one another with T as a common point.
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
Jump to other topics
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
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