## Vector Direction

A GIF Animation

A vector is a quantity which has both magnitude and direction.
Examples of vectors include displacement, velocity, acceleration, and
force. To fully describe one of these vector quantities, it is
necessary to tell both the magnitude and the direction. For instance,
if the velocity of an object were said to be 25 m/s, then the
description of the object's velocity is incomplete; the object could
be moving 25 m/s south, or 25 m/s north or 25 m/s southeast. To fully
describe the object's velocity, both magnitude (25 m/s) and direction
(e.g., south) must be stated.

In order for such descriptions of vector quantities to be useful,
it is important that everyone agree upon how the direction of an
object is described. Most of us are accustomed to the idea that up on
a map refers to the northward direction and right on a map refers to
the eastward direction. This is a mere *convention* which
mapmakers have used for years and upon which we all can agree. But
what is the direction of a vector quantity which is not due north or
due east but somewhere in between north and east? For such cases as
this, it is important that there be some convention for describing
the direction of such a vector. The convention upon which we can all
agree is sometimes referred to as the CCW convention -
**counterclockwise convention**. Using this convention, we can
describe the direction of any vector in terms of its counterclockwise
angle of rotation from due east. The direction north would be at 90
degrees since a vector pointing east would have to be rotated 90
degrees in the counterclockwise direction in order to point north.
The direction of west would be at 180 degrees since a vector pointing
west would have to be rotated 180 degrees in the counterclockwise
direction in order to point west. Further illustrations of the use of
this convention are depicted by the animation below.

For more information on physical descriptions of motion, visit
The Physics Classroom. Detailed
information is available there on the following topics:

Vectors and
Direction
Vector
Addition

Vector
Components

Other animations can be seen at the Multimedia
Physics Studios.

© Tom Henderson, 1996-2007

All Rights Reserved