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The Science of Physics Section 1
UNIT OUTLINE--TOPICS
What is Physics?
Branches of Science
Science Terms
Scientific models
Measuring and Units
Powers of Ten and conversions
Graphing
Experimental Design Science vs. Technology
Analyzing in Physics
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The Science of Physics Section 1Chapter1
OBJECTIVES
List basic SI units and the quantities they describe.
Using prefixes and powers of ten.
Distinguish between accuracy and precision.
Taking good measurements
Use significant figures in measurements and
calculations.
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The Science of Physics Section 2
INTERNATIONAL SYSTEM OF UNITS (SI
UNITS)
Developed for the sake of
consistency
ease of understanding
sharing data
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BASE SI UNITS (STANDARD UNITS)
Measured quantity
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DERIVED UNITS
Derived Units: Combinations of the 7 base units.
Examples
Area (length x width) m x m = m2
Velocity (distance/time) = m/s
10 meters
5 meters50 m2
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The Science of Physics Section 2
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The Science of Physics Section 2Chapter1
NUMBERS AS MEASUREMENTS
In SI, the standard measurement system for science,
there are seven base units.
Each base unit describes a single dimension, such
as length, mass, or time.
The units of length, mass, and time are the meter
(m), kilogram (kg), and second (s), respectively.
Derived units are formed by combining the seven
base units with multiplication or division. Forexample, speeds are typically expressed in units of
meters per second (m/s).
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The Science of Physics Section 2
MEASUREMENTS
Measurements consist
of a number and a unit. Example
100 meters
the number of
units or valuethe unit
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The Science of Physics Section 2Chapter1
DIMENSIONS AND UNITS
Measurements of physical quantities must be
expressed in units that match the dimensions of that
quantity.
In addition to having the correct dimension,measurements used in calculations should also
have the same units.
For example, when
determining area by
multiplying length and width,
be sure the measurements
are expressed in the same
units.
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The Science of Physics Section 2Chapter1
OBJECTIVES
List basic SI units and the quantities they describe.
Using prefixes and powers of ten.
Distinguish between accuracy and precision.
Taking good measurements
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The Science of Physics Section 2Section 2 Measurements inExperimentsChapter1
SI PREFIXES
In SI, units arecombined withprefixes thatsymbolize
certain powersof 10. The mostcommonprefixes andtheir symbolsare shown in the
table.
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The Science of Physics Section 2Chapter1
OBJECTIVES
List basic SI units and the quantities they describe.
Using prefixes and powers of ten.
Distinguish between accuracy and precision.
Taking good measurements
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The Science of Physics Section 2Section 2 Measurements inExperimentsChapter1
Accuracy and Precision
Accuracy is a description of how close ameasurement is to the correct or accepted valueof the quantity measured.
Precision is the degree of exactness of ameasurement.
A numeric measure of confidence in a
measurement or result is known as uncertainty. Alower uncertainty indicates greater confidence.
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The Science of Physics Section 2
ACCURACY
Accuracy is the extent
to which a
measurement
approaches the truevalue.
Your Time:
2:05 pm
Actual Time:
2:10 pm
Your accuracy is off by 5minutes
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The Science of Physics Section 2
ACCURACY AND PRECISION
Precision is the degree
of exactness for a
measurement.
It is a property of theinstrument used.
The length of the pencilcan be estimated totenths of centimeters.
Accuracy is how close
the measurement is to
the correct value.
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The Science of Physics Section 2
ERRORS IN MEASUREMENT Instrument error
Instrument error is caused by using measurementinstruments that are flawed in some way.
Instruments generally have stated accuracies such asaccurate to within 1%.
Method error Method error is caused by poor techniques (see picture
below).
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The Science of Physics Section 2
- THE BULLS EYE REPRESENTS THE TRUE VALUE.- THE DARTS REPRESENT THREE SEPARATE MEASUREMENTS
accurate
less accurate
these darts
show good
accuracy
which paint ball
mark is more
accurate?
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PRECISION
Precision is the degree
of exactness of a
measurement.
Based on the scale of
the measuring
instrument.
Smallest tick marksrepresent millimeters
(mm)
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PRECISION VS. ACCURACY
AGood precision and
accuracy
BSome accuracy
and poor precision
CGood precision and
poor accuracy
DPoor precision and
accuracy
A B C D
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DISCUSSION QUESTION When shooting free throws, is it better to be precise
or accurate?
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The Science of Physics Section 2
Its better to be accurate.
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The Science of Physics Section 2Chapter1
OBJECTIVES
List basic SI units and the quantities they describe.
Using prefixes and powers of ten.
Distinguish between accuracy and precision.
Taking good measurements
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The Science of Physics Section 2
MEASUREMENTS
Dimension - the kind of physical quantity being
measured
Examples: length, mass, time, volume, and so on
Each dimension is measured in specific units. meters, kilograms, seconds, liters, and so on
Derived units are combinations of other units.
m/s, kg/m3, and many others
Scientists use the SI system of measurement.
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The Science of Physics Section 2
HOW TO MEASURE?
Know how to operate the measuring instrument
Which unit(s) is represented?
What does each tick mark represent?
Are there multiple scales? Did you zero out the instrument (if possible)
Be skilled and patient enough to measure with the
greatest detail possible
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WHAT DO THE TICK MARKS REPRESENT
ON A METER STICK? What unit is represented by the smallest tick mark
on the meter stick?
m?
dm?
cm?
mm? *
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WHAT DO THE TICK MARKS REPRESENT
ON A METER STICK? What is the measurement?
In mm?
65 mm
In cm?
6.5 cm
In dm?
.65 dm
In m?
0.065 m?
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WHY SO MANY DIFFERENT UNITS OF MEASUREMENT FOR THESAME QUANTITY?
Consider Mark and Suzy. They want tomeasure the length of a room.
The quantity they are measuring is distance
(measured quantity). They both measure length in units of feet
(the length of one foot) This is theirmeasuring units.
One important detail: Marks foot is longer
than Suzys foot.
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The Science of Physics Section 2
WHY SO MANY DIFFERENT UNITS OF MEASUREMENT FOR THESAME QUANTITY?
Mark measures the length of the room. So doesSuzy. Will they have the same measurement? Whyor why not? Who will have the longer measurementin feet?
Marks measurement is 18 feet and Suzys is 23 feet. The length of a markfoot is not the same as the
length of a suzyfoot.
To compare the two different measurements, oneunit must be converted into the other so that both
measurements are proportional. Standardizing units means to select either the length
of Marks or Suzys foot as the accepted length ofthe unit called a foot.