Review and Graphical Analysis

1
Review and Graphical Analysis

• PVHS Honors Physics

Part 1
2
Essential Questions

• What is Physics?
• What is the scientific method?
• What are the standard units of measure used in
  physics?
• What is Data?
• In measurement, what is the difference between
  accuracy and precision?
• How does one perform calculations using
  scientific notation and significant figures?
• What is the proper way to construct a graph from
  experimental data?
• What is dimensional analysis and how is it used
  to verify the answer to an equation?

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What is Physics?

• Physics is the study of matter and energy
• Physics is the foundation of all sciences

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Fields within Physics

• Mechanics - Study of motion and its causes
• Falling, friction, weight rotation, forces
• Thermodynamics - Heat transfer
• Melting, freezing, engines, refrigerators
• Vibrations and Waves - Repetitive motion
• Sound, springs, pendulums
• Optics Light
• Mirrors, lenses, color, astronomy, lasers
• Electromagnetism- Electricity, magnetism, light
• Circuitry, electromagnets, superconductors
• Relativity Objects moving at high speed
• Quantum mechanics Behavior of microscopic
  particles

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Scientific Method

• Scientists use the Scientific Method to answer
  questions and gather knowledge
• It is a systematic approach
• The method is self correcting through repeated
  observation and experimentation
• Our Labs will generally follow this approach

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Theory and Natural Law

• Natural Law
• Describes HOW nature behaves
• Theory
• Explains WHY nature behaves a certain way
• The most important thing to remember about a
  scientific hypothesis is that it must be
  testable.
• If its not testable, it is not a scientific
  hypothesis.

Observation
Question
Hypothesis
Experiment
Conclusion
Theory (why)
Natural Law (how)
Theory modified as needed
Prediction
Experiment
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Scientific Hypotheses

• Which is a scientific hypothesis?
• Atoms are the smallest particles of matter.
• The universe is surrounded by a second universe
  that cannot be detected.
• Albert Einstein was the greatest physicist of all
  time.

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The Measure of ScienceInternational System (SI
Units)

• SI Units will be used exclusively
• Base Units
• Mass kilogram (kg)
• Length meter (m)
• Time second (s)
• Count, quantity mole (mol)
• Temperature Kelvin (K) or Centigrade (oC)
• Electric current ampere (A)
• Light intensity candela (cd)
• Advantages
• Internationally accepted
• One unit for each physical quantity
• Base 10 prefixes

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Metric PrefixesMost Common
Prefix Abbreviation Meaning
mega- M 1,000,000 or 106
kilo- K 1000 or 103
1
deci- d 0.1 or 10-1
centi- c 0.01 or 10-2
milli- m 0.001 or 10-3
micro- m 0.000 001 or 10-6
nano- n 0.000 000 001 or 10-9
pico- p 0.000 000 000 0001 or 10-12
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Demo

• A hydrogen atom has a diameter of about 10nm.
• What is the diameter in meters?
• Millimeters?
• Micrometers?
• Inches?

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Do

• The wavelength of Red light emitted by a laser is
  about 650nm
• What does nm mean?
• What is the wavelength in meters?
• In kilometers?
• In mm?
• In feet?

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What is data?

• Data is a collection of information or facts
• People need data to make decisions and solve
  problems
• Can you think of any examples of people who use
  data? Have you ever used data?
• Experimental data is data produced by an
  experiment
• Scientists use experimental data to develop or
  prove scientific theories

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What are the types of data?

• There are 2 types of data
• Numerical Data is data that is measured or
  identified on a numerical scale. (measurements)

Unacceptable Table

• Qualitative data is data obtained by observation.
  It includes virtually any information that is not
  measured. (observations)

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Data and Variables

• In an experiment, the data collected are
  generally observations or measurements of a
  variable
• Variable a property of an object or system whose
  value may vary over the course of an experiment
• There are 3 types of variables
• Independent, dependent, and controlled

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Variables

• Independent Variables are changes to properties
  that you, the experimenter, make in order to do
  your experiment
• There is never more than one independent variable
  in a valid experiment
• Dependent Variables are properties that change
  because of changes in the independent variable
• Dependent variables depend on the independent
  variable
• Controlled Variables are other properties that
  could influence the dependent variables
• Must be held constant for a valid experiment

Food Web ????
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Collecting Data

• There is no such thing as a Perfect Measurement
• There is always some source of error
• Method error
• Parallax
• Instrument error
• When judging a measurement you must consider
  Accuracy and Precision
• Accuracy Describes how close a measurement is
  to the standard or true value
• Precision Describes how close each different
  measurements are to one another consistency

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Precise and accurate
This is
Good
Accurate but not precise
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Significant Figures

• Track of the precision of a measurement
• Calculations based on data can only be as precise
  as the worst measurement
• Include the digits actually measured plus an
  estimate

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Significant Figures
Measured digits - Known with certainty
Estimate 1st digit that is uncertain
1.42 cm
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Determining Significant Figures

• All non-zero digits are significant
• All zeros in front of non-zero digits are not
  significant
• All zeros between non-zero digits are significant
• Zeros at the end of a number and to the right of
  the decimal point are significant
• Use the Atlantic-Pacific Rule

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Calculations

• Addition and Subtraction
• Your answer should have the same number of
  significant figures to the right of the decimal
  as the measurement with the least number of
  digits to the right of the decimal

97.3 5.85 103.15
103.2
Round to
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Calculations

• Multiplication or Division
• Answer has the same number of significant figures
  as the measurement with the least number of
  significant figures

123 x 5.35 658.05
658
Round to
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Calculator Use

• Calculators do not take into account significant
  figures you must figure the correct number for
  you answer
• Example
• Round at end 40.
• Round at intermediate steps 41.
• A 2.5 difference
• In this class, carry all digits and round at the
  end.

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Scientific Notation

• Helps keep track of significant digits.
• Use base 10 exponents with one digit to the left
  of the decimal.

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Essential Questions

• What is Physics?
• What is the scientific method?
• What are the standard units of measure used in
  physics?
• What is Data?
• In measurement, what is the difference between
  accuracy and precision?
• How does one perform calculations using
  scientific notation and significant figures?
• What is the proper way to construct a graph from
  experimental data?
• What is dimensional analysis and how is it used
  to verify the answer to an equation?

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Questions?