Transcript PSC 1121 Intro to Physical Science

PSC 1121
Intro to Physical Science
Dr. Jeff Bodart
D008 Natural Science
[email protected]
526-2761 EXT.3252
PSC 1121 Instructor Course Handout
Course Content:
Read textbook
additional material included in lecture
additional material on web site
- not covered well in textbook
- practice problems
Course grade:
Homework and Class Activities 20%
Chapter Exams (5 plus final)
80%
One HW grade dropped
No exam grades dropped
Exams: multiple choice and
problem-solving
concept and numerical problems
Science - understand world around us
•Relate physical quantities to the
environment
•predict from observations
•recognize false reasoning (magicpseudoscience)
•Appreciate technological workings
Historical Background:
NATURAL MOTION
Ancient Greeks - four elements
Natural State: rest
rocks fall-fire rises
F
A
W
E
medium
Adds resistance
to motion - speed
UNNATURAL MOTION
spears, arrows, projectiles
vacuum
medium
ASTRONOMY
Geocentric Universe - Earth Centered
5th element
- aether
World Understood
sun, moon, stars rises in east - sets in west
heavy objects fall faster
thrown rock hits ground and stops
Not science, but made predictions
•Described specific cases
•Why without knowing how
•Qualitative measure - fast, slow
Galileo - Father of Scientific Method
quantitative measurements on inclined plane
- measure time
motion
- measure position
}
d
All objects fall same
Natural state constant speed-uniform motion
More complexity in measurements - telescope
-Moon rough
-Jupiter has moons
-Mars orbit not circular (Tycho Brahe)
Heliocentric (Sun-centered)
Scientific Method
EXPERIMENTATION TO SEE HOW WORLD WORKS
describe and predict quantitatively
make observation
preliminary explanation
predict from explanation
test prediction
modify explanation
LED TO SCIENTISTS - look at various problems
describe how-understand why
Basic (Fundamental) Sciencedescribe and understand
self-testing: test by application
peer review - repeatable
objective - not ugly or beautiful
Science only as good as the observations
Applied Science
ability to predict and exploit nature
electric, gas power
building construction
Tools of Science - made to understand nature
Scientific Law statement based on what is always observed
use to predict unknown outcome from starting point
often mathematical- dependent and independent variables
“what goes up comes down”
usually
Scientific Theory working explanation of why a law is true
not proven, accepted if passes all tests
constant fine-tuning
“gravity acts between two objects with mass”
Scientific model makes a theory easy to understand or use
simple picture of the theory that accounts for
all aspects of the theory
M1
M2
F=G M1*M2/R2
R
Attractive force acts between
centers of spheres
Technology
Applying scientific work to real world situations
APPLIED SCIENCE
Consequences on physical world
Transportation: horse
space shuttle
environmental effects
Technology assessment
-understand consequences in advance
- before too late
DDT, Pollution, OZONE Problem
Technology developed by:
single researchers (basement science)
penicilin, nuclear fission,
liquefaction of H and He
BIG science - large collaborations
university, government, industry
multidisciplinary-phys, chem, bio, eng
many fields to address all aspects
brute force - SHUTTLE, ENERGY
Multinational - modern communications
journals, WWW, email, FAX
access to results of others, peer review
Larger collaborations Larger grants Larger science
Physical Science and Measurement
Taken from Chapter 1 “What is Science?” and
Appendix A “Mathematical Review”
Physical Quantities - measure to quantify
physical properties (qualities or attributes of object)
symbol representations: d, v, F, p
Physical Science
-measure physical quantities
-relate to environment
-predict position, speed, force
energy, voltage,
chemical properties
description has both:
number - how much of a quantity
units - well-defined reference amount
measurement - comparing a property of an object to
a well-defined referent
referent - describes a specific amount of
a property - PHYSICAL STANDARD
STANDARDIZE - measure the same as
everyone else
History : cubit, foot, hand, inch, palm (anatomy)
change over time
new king, wear, disaster
NEED CONSISTENT SYSTEM OF UNITS
ENGLISH CUSTOMARY SYSTEM OF UNITS
MOST COMMON SYSTEM IN USA -foot, pound, second
-changes in parts of world
-now in terms of metric
-not common in rest of world
need a world-wide system for science, trade industry
Metric System ( 1791 )
-based on easily reproduced standards
-quantities measured as number and unit
- meter, gram, second
standard units -a well-defined amount of a physical quantity
1. A quantity that doesn’t change over time
10 million
meters
2. Scheme to measure consistently
length - size of earth
- length of Pt-Ir bar
- speed of light (1/300000000 sec)
time
- mean solar day (24 hours,60 min, 60 s)
- Cs atomic clock
mass - mass of a 1 liter of water
Temperature
sound
color
light intensity
electric current
Conferences to discuss proper units
International bureau of Weights and Measures
meet every 4 years to refine standards
U.S. National Bureau of Standards
Primary standard - reproduction of standard unit
- locked away
Secondary standard - copy of primary to reproduce
commercial copy
US is committed to changing to metric
-voluntary program
-compete internationally
commerce, sports, science
-mixtures of units for transition (confusing)
cars, soda, Olympics, road signs
-must know how to convert between units
1 inch = 2.54 cm
conversion relation
SI System of Units (Systemme Internationale)
M
K
S
units
standardized units used in Physical Sciences
base units - describe fundamental properties
length (m), mass (kg), time (s), temperature (K),
Current (ampere), light intensity (candela), number (mole).
Measuring physical quantities:
relate symbolic quantities (number & unit) to
the circumstances of an object (gravity, external,etc.)
How to deal with numbers (how much)?
Exponential (Scientific) Notation: shorthand way
of dealing with very large or small numbers
Coefficient
1-9.99999
}
7.2x106
exponent-how many decimal
places to move
exponential-shows
power of ten scale
can work with regular numbers(coefficient)
separate from powers of 10
9.76x105 = 9 7 6 0 0 0 .
How does it work....
Examples:
10234=
x10
0.00542 =
x10
342.04 =
x10
289.0 =
x10
Positive exponent >1
Negative exponent <1
4.75x105=
4.03x10-4=
Multiplying and Dividing exponentials
Treat two parts separately:
add exponents
5
3
when
(5.4x10 )(2.34x10 )
multiplying 10’s
5
3
=(5.4 x 2.34)(10 x 10 ))
=12.636 x (10 5+3)
=(1.2636 x 101) x 108
Dividing: divide coefficients separate from exponential
4.28x104
3.5x102
=
4.28
3.5
x
104
102
Subtract exponents
= 1.223 x 104-2 = 1.223x102
Example: (3.6x107) / (6.4x10-3) =
(4.3x10-12) / (7.2x105) =
Or just use calculator: exponential button
EXP or EE
-stands for “times ten to the”
Type in the coefficient, press [EXP or EE] and then the exponent
times/divided
coefficient, [EXP or EE] and exponent
you can try the examples above using your calculator
Multiples and Submultiples - metric prefixes
Different scales of measurement: length
Atoms
10-9
Cells
10-6
Bugs
10-3
People
100
City size
103
To moon
106
To sun
109
-shorthand indicates scale
-don’t have to carry zeros
-agreed upon world wide
-use conversion relation above:
4.2 Mm = 4.2 x (106 m)=4.2x106 m
Dimensional Analysis - manipulating/converting units
36 inches
feet?
conversion relation
relates equality of units
1 foot = 12 inches
1 foot
36 inches x 12 inches=
Example: A pen is measured to be 5.2 inches. What is
the length of the pen in centimeters?
(conversion relation 1 inch = 2.54 cm)
Following units can help problem-solving
Can tell if you run into problems
-units don’t add right
-wrong unit in final answer
-use SI and you get SI
-the right unit is a big part of answer (auto -1)
Accuracy and Significant Figures
Physical quantities are measurements
-limitations on measuring device
-should include uncertainty in measurement
- alternative to showing +/- 0.001 m uncertainty
-uncertainty built into number
- the number of reliably
measured digits plus a guess in the last
SIGNIFICANT FIGURES
2.8
1
2
3
4
The number of digits
describes ruler
5
2.83
Accuracy built
into measurement
1
2
3
4
3
5
2.845
1
2
3
4
5
Rules for significant figures
Determine number of sig figs in a measurement:
1234.56
6 sig figs
rule 1 - all nonzero numbers significant
1.001042
7 sig figs
rule 2 - zeros between sig figs
are significant
4 sig figs
rule 3 - zeros acting as place
holders insignificant
(describe size of ruler)
0.004304
1400000
2 to 7 sig figs
ambiguous answer
use scientific notation to clarify
243.040
3400.0
0.036
Working with Sig Figs
using sig figs while multiplying and dividing
rule 4 - use the least accurate number
of sig figs in final product
or quotient (least sig figs)
Example: 5.347 x 0.0537 =
Use 3 sig figs in final answer (least accurate measurement)