# 1.01 Introduction to measurement theory

## Objectives

In this section you should focus on learning the definitions of all the terms in bold and be able to recall the five base dimensions.

## Introduction

Measurement is one of the fundamental activities involved in physical sciences. Measurement allows us to quantify properties such as mass, time and length etc. (Quantify simply means to express the magnitude (size) of the quantity with a numerical value. e.g. Expressing someone's height as say 1.8m would be an example of quantifying height as opposed to say simply describing the person as "tall".) In order to quantify a property we need to use suitable units of measurement (such as metres seconds etc.)

In physical science the term quantity is used both in its normal sense (i.e. to simply mean "amount") and also to refer to a measureable property (e.g. time, length, temperature etc). These measureable properties are usually (but not always*) the physical properties of an object (i.e. they are usually physical quantities such as mass length etc.) (*some of the things we measure such as angles are not strictly speaking physical quantities - see later)

## Base Dimensions

There are five fundamental physical properties that can be measured these are • Length (L)
• Time (T)
• Mass (M)
• Electrical Charge (Q)
• Temperature (Θ)

We call these fundamental properties the five base dimensions

All other physical properties can be broken down into different combinations of these five base dimensions. e.g. :-
velocity = length/time (L/T)
density = mass/volume (M/L3)