# M1 OCR: Vectors, Forces and Friction

Topic 1 of the OCR M1 A Level

- Created by: Ayesha
- Created on: 28-05-12 09:26

First 240 words of the document:

Mechanics

1. Vectors, Forces and Friction

Vectors have magnitude and direction

To find the resultant force, line up all the forces

tip to tail and connect them up

Use the sine / cosine rules and rules about

angles and parallel lines

Remember for bearings go clockwise

Unit Vectors

o Vector of magnitude 1

o Make components of the vector: i and j

o X direction: i

o Y direction: j

o E.g. if you have a vector 16i + 12j with a

magnitude 20, the unit vector is 1/20 (16i + 12j)

or 0.8i + 0.6j

When adding vectors: just add the i and j

components

o E.g. A = 3i + 2j plus B = 5i 6j

o A + B = 8i 4j

o To find the resultant force of A + B, make a

Pythagorean triangle

Making components

o X axis: v cos

o Y axis: v sin

o V = v cos i + v sin j

If a force is applied vertically it doesn't apply

at all horizontally and vice versa

If a force is applied at an angle then it is

applied vertically and horizontally

o Vertical component: F sin

o Horizontal component: F cos

On an inclined plane, resolve parallel and

perpendicular to the slope

o Weight acts straight downwards

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