SCALAR AND VECTOR QUANTITIES
Figure 2 Vector
To help distinguish between a scalar and a vector, let's look at an example where the only
information known is that a car is moving at 50 miles per hour. The information given (50 mph)
only refers to the car's speed, which is a scalar quantity. It does not indicate the direction the
car is moving. However, the same car traveling at 50 mph due east indicates the velocity of the
car because it has magnitude (50 mph) and direction (due east); therefore, a vector is indicated.
When a vector is diagrammed, a straight line is drawn to show the unit of length. An arrow is
drawn on one end of the line. The length of the line represents the magnitude of the vector, and
the arrow represents the direction of the vector.
Description of a Simple Vector
Vectors are simple straight lines used to illustrate the direction and magnitude of certain
quantities. Vectors have a starting point at one end (tail) and an arrow at the opposite end
(head), as shown in Figure 2.
Examples of Vector Quantities
Displacement, velocity, acceleration, and force are examples of vector quantities. Momentum
and magnetic field strength are also good examples of vector quantities, although somewhat
more difficult to understand. In each of these examples, the main ingredients of magnitude and
direction are present.