Vectors and Scalars
Most things we encounter in Physics are either scalars or vectors.
A scalar quantity has only magnitude and no direction.
This means we can fully explain a scalar with a number and a unit:
Water freezes at a temperature of 0o C or 32O F
The mass of an air track glider is 198.2 g
The length of an air track is 2 m
The weight fell for a time of 0.55 s
The block's kinetic energy was 0.345 J
A vector quantity has both magnitude and direction.
The wind had a velocity of 25 km/h from the North
Champaign is about 80 km north of here
The momentum was 1.234 kg m/s to the left
The distinction between scalars and vectors is important. We will use bold face type to indicate a vector, such as r. In writing a vector by hand, we will indicate a quantity is a vector by drawing an arrow above it as
. Some such distinguising notation is important. Do not write a vector without some distinguishing characteristic or notation.
(c) Doug Davis, 2001; all rights reserved