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Chapter 1 Introduction, Measurement,
estimating
Reading Guide Due ___________
Vocabulary Due ____________
Problems Due _____________
Approximate Test Date ________
Chapter Important Dates
Models, Theories, and LawsModel - a mental or visual image
- can be a picture, diagram, or graph- relates something we don't understand to something we do- should simplify a problem A theory CAN NEVER be proved,
ONLY disprovedA theory CAN be ACCEPTED if it:
stands up to experimental testingis more accurate than previous theoriesexplains more situations than previous theories
Theory - any idea that attempts to explain an observation- can be a concept or a mathematical relationship
Laws Universally accepted generalizations of observed physical behavior
Most laws are written as
mathematical equations called formulas
Laws must be experimentally validover a large range of conditions
Physical laws are DESCRIPTIVE
They DESCRIBE how an object is expected to behave
THEY DO NOT CONTROL HOW AN OBJECT BEHAVES.
Measurement
Precision is the ability to get the same result over and over.
Accuracy is how close the result is to the actual answer.
A good measurement in Physics is BOTH accurate and precise.
Measurements and Errors
EVERY measuring tool is limited in it's ability to measure accurately and precisely.
Measure the line below.
0 1 2
0 1 2 3 4 5 6 70°
What are possible causes of errors?
Do these errors limit your precision or your accuracy?
These errors are estimated to be ± half of the smallest increment shown.
Measure the same line with two different rulers. Do you get the same answer?
Is this an error in precision or accuracy?
This value is determined by the manufacturer.
Every measuring tool is manufactured to a different standard.
The estimated uncertainty is the sum of the precision error and the accuracy error.
What is the ESTIMATED UNCERTAINTY for the protractor and the ruler?
0
1
2
3
4
5
6
0
1
2
90°
0 180
10 170
20160
30
15040
14050
13060
120
70
110
80
100
90
90
0°
100
80
110
70
120
60
130
50
140
40
150
30
16020
17010
1800
0 1 2 3
0 1 2 3 4 5 6 70°
How to Write Estimated Uncertainty & What it means
Measure each line. Write the answer including the estimated uncertainty.
What are the possible actual lengths of each line?
Percent Error -How big is the error compared to the measurement?
Find the percent error for the given angle:
Significant Figures - In science, we recognize the limitations of our measurements.
We can only use as many digits as we can accurately measure.
Use Percent Error to help decide how many digits to use.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
0 1 2 3 4 50°
Identifying Significant Figures - How many Significant Figures are in each of the following numbers?
6.45
450
7340.0
0.0063
0.0140
50.205
In large numbers, zeros to the RIGHT of the last nonzero digit ARE NOT significant
Unless they are continued TO THE RIGHT of the decimal
In decimals, zeros to the left of the first nonzero digit are not significantZeros to the RIGHT of DECIMALS
ARE significant figuresZeros BETWEEN nonzero digits are
ALWAYS significant
NONZERO digits are ALWAYS significant
Working with Significant FiguresAdding and Subtracting
The number of digits is limited to the least accurate DECIMAL
POINT
Add: 2.34 + 0 .035Multiplying and Dividing
The number of digits is limited to the least number of significant figures
Multiply: 0.21 * 5.07
Take this example:Anna is 17 years old. How old is she in seconds?
536112000 Seconds.
When is Anna exactly 536112000 seconds old?Is she that old now?How many significant figures should you use?
Calculate.Give each answer with the correct number of significant figures.
2.75 * 0.043 9.464 56.2
56.78 + 2.024 2600 / 0.0345
52 / 3.30 58001 * 1.00257
For multi-step calculations keepALL digits until the very end.
This can affect ROUNDING 82.354 + 53.2/1.254
Calculate.Give each answer with the correct number of significant figures.
25.34 * 0.0124 8.74
5.46 / 2.15 + 2.12 * 120
Scientific Notation-easily write and compare very large & very small numbers -only write the significant digits
-only ONE digit in front of the decimal place
-Order of Magnitude changes the Decimal Place
Orders of Magnitude
Write in decimal notation.2.34 x 104
2.34 x 10,000
23,400
5.72 x 105
5.72 x 0.00001
0.0000572Positive Exponents -
A LARGE NUMBERThe decimal moves to the RIGHT
the number of places in the exponent
Negative Exponents - A SMALL NUMBER
The decimal moves to the LEFTthe number of places in the exponent
Write in decimal notation.2.56 X 103
3.24 X 1014 X 1010
55.7 X 107
5.8 X 100
0.1483 X 101
Write in Scientific Notation
54,800
Large Numbers Positive Exponents,Decimal Moves to the LEFT
5.48 X 10464.78 X 10354,800
6.478 X 103+1
6.478 X 104
64.78 X 103
78.2 X 105345 X 101Write in Scientific & Decimal Notation
78.2 X 105345 X 101
7.82 X 105+13.45 X 101+2
7.82 X 1043.45 X 101
Decimal Notation
Scientific Notation
.00078234.5
0.00002478
2.478 X 105
Small Numbers Negative Exponents, Decimal move to the Right
0.00002478 0.0843 X 1070.0843 X 107
8.43 X 1072
8.43 X 105
Write in Scientific Notation Write in Scientific & Decimal Notation0.0045 X 104 0.000579 X 104
Decimal Notation
Scientific Notation
4.5 X 1043
0.0045 X 104
4.5 X 107
0.00000045
5.79 X 1044
0.000579 X 104
5.79 X 100
5.79
Write in Scientific Notation35,000,000,000 0.0004874
0.0487 X 108
10.078 X 1016
0.000142 X 102
2040 X 103
Calculations in Scientific Notation-Adding & Subtracting Numbers must have the same
Order of Magnitude
Add or Subtract Normally, Keep the Order of Magnitude
Use the correct number of Significant Figures!
Adjust answer to maintain Scientific Notation
6.24 X 1012 + 5.76 X 1012
(6.24 + 5.76) X 10126.24 X 1012 + 5.76 X 1012
12.00 X 1012
1.200 X 1012+1
1.200 X 1013
Calculations in Scientific Notation-Adding & Subtracting
2.71 X 105 + 5.48 X 103
If the Exponents do not match, adjust the SMALLER VALUE to match the LARGER VALUE.
0.0271 X 105+2 + 5.48 X 103
0.0271 X 103 + 5.48 X 103 Positive adjust left,Negative
adjust right.
NOTE:
(0.0271 + 5.48) X 103
5.5071 X 103
5.51 X 103
2.71 X 105 + 5.48 X 103
Calculations in Scientific Notation-Adding & Subtracting
Calculations in Scientific Notation-Multiplying & Dividing
Multiply or Divide the numbers normally.
Multiply or Divide the Order of Magnitude separately.
Use Exponent Rules Multiply add exponentsDivide subtract exponents
Use the correct number of Significant Figures!
Adjust the answer to Scientific Notation.
Calculations in Scientific Notation-Multiplying & Dividing
(3.4 X 1011)(4.21 X 107)
(3.4 * 4.21) X (1011*107)
14.314 X 1011+7
14 X 1018
1.4 X 1019
(3.4 X 1011)(4.21 X 107)
Calculations in Scientific Notation-Multiplying & Dividing
(5.47 X 103) ÷ (7.23 X 107)
(5.47 ÷ 7.23) X (103 ÷ 107)
(0.756570...) X (1037)0.757 X 104
7.57 X 105
(5.47 X 103) ÷ (7.23 X 107)
Calculate(1.542 X 102) + (5.4 X 101)
(7.4 X 104)(3.34 X 102)
Calculate(5.734 X 105)÷(4.04 X 102)
(8.4 X 102)-(7.24 X 103)
Calculate(2.04 X 104) + (5.467 X 102)
(7.3 X 1012)(2.4 X 1013)
Scientific Notation with Graphing Calculators Systems of MeasurementTwo Main Systems of Measurement
British Engineering System
Systèmè International
Used Primarily in the USRarely used in Britain
Used around the WorldPreferred for Scientific Studies
inches, feet, yards, milesfl. oz, cups, pints, quarts, gallons
slugounces, pounds, tons
seconds, minutes, hours
centimeter, meter, kilometermilliliter, liter
milligrams, grams, kilogramsNewtons
seconds, minutes, hours
Systems of MeasurementBASE UNITS ARE DEFINED BY STANDARDS
Length, Time, Mass, Current, Temperature, Amount, Luminous Intensity
DERIVED UNITS CAN BE DEFINED IN TERMS OF BASE UNITS
Area, Volume, Speed Acceleration, Weight/Force,
Work, etc.
.
Systems of Measurement - LengthBase Unit (SI)- Meter(m) -
Defined in the 1790s as the
distance from the equator to either pole
Once defined by the length of a man's foot
Now one foot is defined as 0.3048 m
Base Unit (British) - foot(ft.) -
Approximate Lengths in Meters(order of magnitude)
Arm Span 100
Atom 1010 Football Field Length 102
Paper Thickness 104 Earth Diameter 107
Penny Thickness 103 Earth to Sun 1011
Penny Diameter 102 Earth nearest galaxy 1022
See also, Textbook pg 8 Table 1-1
Systems of Measurement - TimeBase Unit (SI & British)- second(s) - Originally defined as of the average day.
Now defined based on the radiation of cesium atoms.
Approximate Times in Seconds(order of magnitude)
Heartbeat 100Humans on Earth 1014
One Day 105Age of Universe 1018
3 Years 108
See also, Textbook pg 9 Table 1-2
Systems of Measurement - MassBase Unit (SI)- kilogram (kg) -
Defined as the mass of a specific platinum‐iridium cylinder kept at the International Bureau of Weights and Measures near Paris, France
unified atomic mass(u)For VERY small masses (atoms and molecules)
approximately the mass of a single proton or neutron 1.6605 X 10‐27 kg
Base Unit (British) - slug - NOT COMMONLY USED
Systems of Measurement - Mass vs. Weight
Mass and Weight ARE NOT the same thingbut they are proportional.
Mass the measure of how many neutrons, protons, and
electrons, etc. are present in an object
changes in gravity DO NOT affect an object's mass
Weighta measure of FORCE
It is a derived unit based on an objects mass AND the amount of gravity it is
experiencing
changes in gravity DO affect an object's weight
Approximate Masses in kg(order of magnitude)
Your Textbook 100
Electron 1030 one year old baby 101
Proton 1027 220 pound man 102
Penny 103 Earth 6 X 1024
See also, Textbook pg 9 Table 1-3
Converting Units-In order to compare or add two or more
measurements they must have the SAME unit
We adjust a measurement to a different unit by a process called UNIT CONVERSION.
Conversion Factors (defined values) tell you how many of one unit are in an equal amount of a second unit.
Converting Units - SIMeasurements are coverted
within the SI system by adjusting the Order of Magnitude,
the number does not change!!!
All units work with the same prefixes.
Time is the only unit that is slightly different
Converting Units - SI
ONE of
these
equalsthis many BASE UNITSg, m, s, L
Convert.300 kg to g 2 km to cm
300 kg 103 g1 kg
300 X 103
300,000 g or
3.00 X 105g
2 km 103 m1 km
1 cm102 m
103102
2
2 X 103 (2)
2 X 105cmor
200,000 cm
Convert.1.5 ns to μs 3 L to mL
42.7 V to kV 78400 mC to kC
Converting Units - Time (both systems)Anything SMALLER than 1 second works the same as the SI system
Larger periods of time have familiar units.1 minute(min) = 60 seconds1 hour(hr) = 60 minutes
1 day= 24 hours
How many hours are in 5.68 X 1012 ms?
1 year(yr) = 365 Days1 Century = 100 Years
1 Millenium = 1000 Years
5.68 X 1012 ms1 ms 103 s 1 min
60 s 60 min1 hr
1.58 X 106 hr
Converting Units- British Common ConversionsLength
1 foot = 12 inches1 yard = 3 feet
1 mile = 5,280 feet
Weight1 pound = 16 ounces1 ton = 2000 pounds
Weight on earth to Mass1 slug = 32 lbs
Volume1 gallon = 4 quarts = 231 in3
1 quart = 2 pints1 pint = 2 cups
1 cup = 8 fluid ounces
Convert.2500 fl oz to gallons2500 fl oz 1 cup
8 fl oz1 pint2 cups
1 quart2 pints
1 gallon4 quarts
39 gallons
1.00 X 102 miles to inches
1.00 X 102 miles 5280 ft1 mile
12 in1 ft
634 in
Converting Units- British SI Length 1 in = 2.54 cm
Mass 1kg = 0.0685 slugs 1 kg = 2.2 lbs on earth
Force 1 lb = 4.45 N
Volume 1 gal = 3.785 L
Work 1 J = 0.738 ft lb
Convert.5 km to miles
265 mL to fl oz
5 km
5 km to miles
5 km 103 m1 km
1 cm102 m
1 in2.54 cm
1ft12 in
1 mile5280 ft
3.11 miles
265 mL 103 L1 mL
1 gal3.785 L
4 qt1 gal
2 pints1 qt
2 cups1 pints
8 fl oz1 cups
8.96 fl oz
Convert.35 mm to inches
4 lb to g (on earth)
Convert.5 quarts to liters
500 slugs to grams
Derived UnitsMany properties have units that are a
combinations of more than one base unit. Mathematically, units are treated the same way variables are.
For Example:Find the area of a 3 foot by 2 foot table.
Area = length * widthArea = 3ft * 2ftArea = 6 ft2
Find the volume of a cube with a side of 3 cm.
Volume = side3Volume = (3 cm)3Volume = 27 cm3
Some derived units we will use in this class.
Derived Units
Quantity SI Derived Base Measurements SI Base Unit Units
Velocity Distance / Time m/s
Acceleration Distance / Time2 m/s2
Force Newton (N) Mass * Distance/ Time2 kg m/s2
Work Joule (J) Mass * Distance2/Time2 kg m2/s2
Power Watts (W) Mass * Distance2/Time3 kg m2/s3
Pressure Pascal (Pa) Mass /(Distance*Time2) kg/(ms2)
( ) 2Converting Derived UnitsConvert65 in2 to ft2 65 in2 1ft
12 in
65 in2 1 ft2144 in2
0.45 ft2
20 m/s to mi/hr
20 m s
1 km103 m
1 mi1.609 km
60 s1 min
60 min1 hr
45 mi/h
6 kg*ms2 ( ) 239.37 in
1 m3600 s1 hr
0.0685 slug 1 kg
Converting Derived UnitsConvert6 kg*m/s2 to slug*in/hr2
2 X 108 slug * in/hr2
Converting Derived UnitsConvert50 ft*lb to N*m 75 km/hr to mi/hr
24 kg*m2/s3 to g*cm2/min3
EstimatingAn estimate can be used to make
calculations easier in cases when knowing an exact answer is not important.
Estimating can also be used to check if an exact answer is reasonable.
A pool is 42 ft long and 18 ft wide. One end is 3 ft deep and the other end is 10 ft deep. The instructions on the chlorine says to add one scoop per 500 gallons of water.
How many scoops do you put in?
Estimate 40 206
40*20*6/5004800/5005000/500
10
Delta thinks that 2850 people will need to fly from Atlanta to Mobile on an average Friday. Each plane holds between 80 and 130 people. How many flights should they schedule?
Estimate 3000
100
3000/10030