CHAPTER 1: THE PHYSICS TOOL KITSections 1.1 and 1.2

The Physics Tool Kit: Ch1, Sections 1 and 2

Objectives

Explain the need for standardization of measurement.

Use the metric and English systems of measurement.

Introduction

The physics student must be able to: Analyze a problem Choose a correct concept formula Manipulate an equation

This chapter gives the basic tools for a physics student. Math techniques Significant digits Accuracy and precision Problem solving strategy

1.1 Standards of Measure

Standard of measure – sets units of measurement for length, weight, and other quantities defined in a way that is useful to a large number of people.

Some interesting historical measurement standards. http://

en.wikipedia.org/wiki/Pottle

Chain – 100 links used for surveying = 66 ft

Rod – 16 men lined up foot to foot; now standardized to 16 1/2 feet

Yard – tip of king’s nose to fingertips of outstretched hand.

Foot – rod divided by 16; was also common to use length of one’s own foot.

Inch – was the length of three barely corns.

US system, sometime called English system, of measurements is a combination of Anglo-Saxon, Roman, and French-Norman weights and measures.

In 1790’s, a decimal system based on the metric system was developed in France Many nations began adopting as official

measurement system. By 1970, the US was the only non-metric

industrialized nation.

Lost in Space http://www.cnn.com/TECH/space/9909/30/mars.metric/

Many businesses, industry and government agencies in the US have now converted voluntarily to the metric system.

In many industries, you – the student and worker – will need to know and use both.

1.2 Introduction to the Metric System SI System of measurement is based

on metric system Gabriel Mouton (1618-1694) System is based on factors of 10

Units are made bigger or smaller by using SI prefixes

SI Base Units

Basic Unit SI Abbreviation Quantity Measured

meter m length

kilogram kg mass

second s time

ampere A electric current

Kelvin K temperature

candela cd light intensity

mole mol amount

SI Derived Units

Derived Unit Abbreviation Quantity Measured

liter L of l volume

cubic meter m3 volume

square meter m2 area

Newton N force

meter per second m/s speed

Joule J energy

watt W power

SI PrefixesMultiple Power of 10 Prefix Prefix

Symbol

1 000 000 000 000

1012 tera T

1 000 000 000 109 giga G

1 000 000 106 mega M

1000 103 kilo k

100 102 hecto h

10 101 deka da

1 100 (base) -

0.1 10-1 deci d

0.01 10-2 centi c

0.001 10-3 milli m

0.000 001 10-6 micro

0.000 000 001 10-9 nano

0.000 000 000 001

10-12 pico p

System Length Time Mass Force & Weight

English foot (ft) second (s)

slug pound (lb)

SI meter (m)

second (s)

kilogram (kg)

Newton (N)

1 lb = 16 ounces (oz) 1 kg weighs 9.80 N or 2.2 lb

1 lb = 4.45 N 1 slug weighs 32.2 lb

1 kg = 1000 g 1 slug = 14.59 kg

Comparison of English and SI Units

Weight and Mass Conversions