The magnitude of a vector is represented by the length of the arrow.
The arrow length is drawn according a chosen scale.
For example, the diagram shows a vector with a magnitude of 100 kilometers, if the scale used for constructing the diagram is 1 cm = 10 km, the vector arrow is drawn with a length of 10 cm.
The arrow has an obvious tail and arrowhead. The arrow points in the precise direction.
Scalar quantities have only magnitude whereas vector quantities have both magnitude and direction. Speed is a scalar quality whereas velocity is a vector quantity as velocity has both a magnitude and direction. Vectors are represented by a line with an arrow head. The magnitude of the vector is represented by the length of the line and the arrow head points to the direction of the vector.
