Review and Graphical Analysis PVHS Honors Physics Part 1

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?

What is Physics?  Physics is the study of matter and energy  Physics is the foundation of all sciences

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

Scientific Method Observation Question Hypothesis Experiment Conclusion  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

Theory and Natural Law  Natural Law Describes HOW nature behaves Describes HOW nature behaves  Theory Explains WHY nature behaves a certain way 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. If its not testable, it is not a scientific hypothesis. Observation Question Hypothesis Experiment Conclusion Theory (why) Natural Law (how) Prediction Experiment Theory modified as needed

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

The Measure of Science International 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 ( o C) Electric current – ampere (A) Light intensity – candela (cd)  Advantages Internationally accepted Internationally accepted One unit for each physical quantity One unit for each physical quantity Base 10… prefixes Base 10… prefixes

Metric Prefixes Most Common PrefixAbbreviationMeaning mega-M 1,000,000 or 10 6 kilo-K 1000 or deci-d 0.1 or centi-c 0.01 or milli-m or micro- or nano-n or pico-p or

Demo… 1.A hydrogen atom has a diameter of about 10nm. a)What is the diameter in meters? b)Millimeters? c)Micrometers? d)Inches?

Do… 2.The wavelength of Red light emitted by a laser is about 650nm… a)What does “nm” mean? b)What is the wavelength in meters? c)In kilometers? d)In  m? e)In feet?

What is data?  Data is a collection of information or facts People need data to make decisions and solve problems 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? 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 Scientists use experimental data to develop or prove scientific theories

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

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 Independent, dependent, and controlled

Variables 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 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 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 Must be held constant for a valid experiment Food Web ????

Collecting Data  There is no such thing as a Perfect Measurement…  There is always some source of error Method error… Method error… Parallax… Parallax… Instrument error… 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 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 Precision… Describes how close each different measurements are to one another… consistency

Neither… Useless Accurate but not precise… Precise but not accurate… Precise and accurate… This is Good

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

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

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…

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 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 Round to 103.2

Calculations  Multiplication or Division Answer has the same number of significant figures as the measurement with the least number of significant figures Answer has the same number of significant figures as the measurement with the least number of significant figures 123 x Round to 658

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 end… 40. Round at intermediate steps… 41. Round at intermediate steps… 41. A 2.5% difference A 2.5% difference  In this class, carry all digits and round at the end.

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

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?

Questions?