# Physics - Combining Vectors

> Source: https://ollybritton.com/notes/a-level/physics/topics/combining-vectors/ · Updated: 2020-09-21 · Tags: ankify, school, physics, year-1

# Combining Vectors
> Combining Vectors is [Physics - Resolving Vectors](https://ollybritton.com/notes/a-level/physics/topics/resolving-vectors/) in reverse, or vice-versa.

##### What is the golden rule for adding vectors??
Always add vectors tip to tail.

##### Combine these vectors, a boat moving $10kmh^{-1}$ across a $10kmh^{-1}$ flowing river PHOTO??
PHOTO
* $\sqrt{10^2 + 10^2} = \sqrt{200} = 10\sqrt{2} kmh^{-1}$

##### When can Pythagoras be used to combine two vectors??
When two known forces are at a right angle.

##### How can you work out the angle between two forces??
Using trigonometry.

##### Visualise a diagram for a train travelling along a $2^{\circ}$ towards a $200m$ summit??
PHOTO

##### How could you find the length of the slope in this diagram PHOTO??
* $\sin 2 \circ = \frac{200}{x}$
* $x = \frac{200}{\sin 2 \circ}$

---
Olly Britton — https://ollybritton.com. Machine-readable index: https://ollybritton.com/llms.txt