Vectors in 3 Dimensions (OCR A Level Maths A): Revision Note
Exam code: H240
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Vectors in 3 dimensions
What is a 3D vector?
Vectors represent a movement of a certain magnitude (size) in a given direction
You should have already come across (2D) vectors at AS (see Basic Vectors)
3D vectors describe the position of a point in a 3D space in relation to the origin
They can be represented in different ways such as a column vector or in i, j, k unit vector form

Magnitude of a 3D vector
The magnitude of a 3D vector is simply its size
Like 2D vectors we can find the magnitude using Pythagoras’ theorem (see Magnitude Direction)

For 3D position vectors we can find the distance between two points
By using the respective co-ordinates we can calculate the magnitude of the vector between them:

3D vector addition, scalars, parallel vectors and unit vectors
3D vectors work in the same way as 2D vectors, just in three dimensions rather than two
Vector addition and subtraction and scalar multiplication can be carried out in exactly the same way, this time involving i, j and k or x, y and z
3D vectors are also parallel if one is a multiple of the other

Unit vectors in 3D are found in exactly the same way as in 2D


Worked Example

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