Applied Physics Chap 1 Introduction 1 Chapter 1: Introduction The nature of science and measurements

Applied Physics Chap 1 Introduction 2 Searching for objective data. Objectivity : The gathering of data or information without preconceived ideas (prejudice) about how something is supposed to be. Experiment: An organized procedure for gathering the data necessary to test a hypothesis. Data Table : an organized method of displaying data. DayTrucksCars Monday1525 Tuesday1230 Wednesday1622 Thursday2126

Applied Physics Chap 1 Introduction 3 Types of Information used in science Data : measurable information learned by conducting an experiment, often in numerical form Constant : factor whose value does not change. Variable : any measurable quantity that may have different numerical values. Control : factors in the experiment that are purposely left constant so that the result of other changes can be seen more clearly. Models : representations of an object or problem developed by simplifying the object or eliminating several variables in order to study parts of an event.

Applied Physics Chap 1 Introduction 4 Line Graphs: are often used to describe how things change over a period of time.

Applied Physics Chap 1 Introduction 5 Are useful for comparing different things that occur at the same time. Bar Graphs.

Applied Physics Chap 1 Introduction 6 Graphing Data: using a Line Graph. Line Graph: points are plotted on the graph and joined together by a line. Time, hours Variable TITLE: Scale Best used to show how changes in value during the course of the experiment Temp 0 C variable

Applied Physics Chap 1 Introduction 7 Measurement: the use of a pre-determined scale as a comparison to observe the size or the amount of something.  Scientists in the ’s realized that accuracy in measurements was the key to uncovering truth about the universe.  As better and more accurate measurement equipment became available, scientists were able to develop clearer understandings about the nature of our universe. Standard of Measure: A numerical quantity that everyone agrees to use, to represent the size or quantity of something. Measurements:

Applied Physics Chap 1 Introduction 8 Customary (or English) system: developed over the centuries and is now used only in the U.S. Metric System: based on units of 10 and developed in the mid 1700’s in Europe and is now used all over the world for commerce and manufacturing. International System SI: a simplified and version of the metric system adopted in the 1960’s to be the measurement system used in physics. Systems of Measure: There are three primary measurement systems in use today.

Applied Physics Chap 1 Introduction 9 Standard Base Units for measurements in both the Metric and SI systems Length : the distance between two points measured in “ Meters ”. Mass : the quantity of matter in an object, measured in “ grams ” Time : the duration of an event measured in “ seconds Temperature : the amount of energy in a substance. Measured in degrees Celsius or degrees Kelvin. Electrical Current : the number of electrical charges flowing through a wire in a second. Volume : The amount of space occupied by an object or substance. measured in Liters or milliliters

Applied Physics Chap 1 Introduction 10 Derived Units: many of the units we work with will be combinations of the basic physical measurement units. Example: m/s means meter divided by second or meter per second, a speed. Example: g/cm 3 means grams divided by cubic centimeters a density measurement

Applied Physics Chap 1 Introduction 11 Working with METRIC Measures: Metric Prefixes: Letters preceding a metric unit like meter or gram that describe the size of the unit: Commonly Used Prefixes. Prefixsymbolmeaningmultiple of base unit Kilo kthousand Deci dtenth. 1. Centi chundreth.01 Milli mthousandth.001

Applied Physics Chap 1 Introduction 12 A single word, like 35.3 meters, 12.0 seconds, or 7.5 liters is always the base unit and its abbreviation is usually a single letter: example: m for meter, g for gram, or s for second. the prefix, when needed, gives the size and always comes first: example: kilometer, centimeter. Abbreviations for measures with prefixes use 2 letters prefix first then the base unit. example: mm the first letter m is for milli and the second m is for meter. Metric Measurements and abbreviations

Applied Physics Chap 1 Introduction 13

Applied Physics Chap 1 Introduction 14 O centimeters O meters O millimeters Metric Rulers can be used for different measures47 mm 4.7 cm.047 m

Applied Physics Chap 1 Introduction 15  Estimate the value between the two marks on either side of the object.  The rightmost digit in your measurement should be an estimated digit mm mm 22 mm 23 mm Hints for making measurements:  Read the scale from left to right.  Start with the mark immediately to the left of the item you are measuring and note its value.

Applied Physics Chap 1 Introduction 16 Rounding off numbers Round to the nearest ten. Step 1: identify the digit in the tens’ place Step 2: look at the digit 1 place to the right If this digit is 5 – 9 round the tens place up If this digit is 0 – 4 do not change the tens place Step 3: Round the tens place up and use a zero as place holder for the 1’s place. 240 would be correct.

Applied Physics Chap 1 Introduction 17 Positive Exponents Exponent of 10 is the number of zero’s after 1 Example: 10 3 = 1000 Zero Exponent: 10 0 = 1 Negative Exponents Exponent of 10 is 1 divided by the number. Multiplying or a number times a power of ten

Applied Physics Chap 1 Introduction 18 Scientific Notation: Representing very large or small numbers using powers of ten. Must be a number between 1 and 9 a decimal point and other digits followed by a power of ten. Example: is represented by 2.34 x or 2.34 x Place decimal point here Count these digits as the power of 10 = 4

Applied Physics Chap 1 Introduction 19 Example: is represented by 4.56 x 10 – Place decimal point here Count these decimal places as a negative exponent –3 Scientific Notation with negative exponents