## Vectors and Scalars

Most things we encounter in Physics are either

scalarsorvectors.## A scalar quantity has only magnitude and no direction.

This means we can fully explain a

scalarwith a number and a unit:Water freezes at a temperature of 0

^{o}C or 32^{O}FThe 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

vectorquantity 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 isimportant.Do not write a vector without some distinguishing characteristic or notation.

(c) Doug Davis, 2001; all rights reserved