Vector is defined as wich quantity that has both a magnitude and a direction. Non-vector is defined a quantity which has only a magnitude. Therefore all physical quantities can be divided into two categories. They are vectors and non-vectors. The length, mass and time are the non-vectors, and the mass, power, and velocity are the vector quantities. Think of the difference between these two types.

Example as a vector quantity. Consider the distance and displacement between two traveling cities shown as the fig. The shortest distance between the two cities is AB. It is only available in a straight line with a direction. It has a direction and a magnitude.

Therefore it is really a vector. The indirect curve, brown colored in various directions, is a route to the city between A and B. This is a non-vector quantity because it’s direction is changed by itself. It has only a magnitude.

## Expressing of a vector

The diagram above depicts as a vector. is the magnitude of the vector . over line represents it as a vector.

## Adding vectors (Parallelogram Method)

Draw the **a** and **b** so that their initial points coincide. Then draw lines to form a complete parallelogram. The resultant of **a** + **b** is the diagonal from the initial point “O” to the opposite vertex “C” of the parallelogram.

## Adding vectors (Triangle Method)

Draw the vector **b** after **a**, placing the initial point of vector **b**** **at the terminal point of vector a. Then draw the resultant from the initial point of vector **a** to the terminal point of the vector **b**. This method is also called the head-to-tail method. You can see the vector **a** + **b** is green colored line OC.

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