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 0^o C or 32^o 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.

Coordinates			Properties of Vectors
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(c) 2005, Doug Davis; all rights reserved