Physics: The Science of Energy - Chapter 1 Notes

1. Physics - Chapter 1 NotesPhysics the Science of Energy Mr. Seaney Ch. 1

2. The Method of Science • Science Permeates every aspect of daily life • Science- the search for relationships that explain and predict nature. • Engineering / technology – The use of science to meet human needs • Scientific Law – A statement that describes the relationship between various phenomena. Widely accepted and thoroughly tested. • Theory- A reasonable explanation of observed events that are related. Generally accepted and widely tested. Often involves models and can be used to predict future behavior

3. The Method of Science cont… • Hypothesis- Possible solution to a scientific problem. • All hypotheses, theories, and laws have inherent uncertainty. All can be disproved by a single crucial experiment.

4. What is Physics? • The study of energy and its transformations • Matter –Anything that has mass and inertia. • All matter has specific properties that can be measured. • Mass- amount of material in an object • Inertia- Property that opposes any change in its state of motion • Mass Density- mass per unit volume • Energy – The capacity to do work • Potential energy – Stored energy based on position of object or molecules • Kinetic Energy – Energy based on relative motion to an arbitrary stationary point. Earth’s surface is considered to be stationary. • Law of Conservation of energy – energy can be changed from one form to another without loss. • E=mc2 - mass and energy can be considered equivalent to one another

5. The Scientific Method • A way to answer questions and solve problems • Steps in the Scientific Method • Observation – Curiosity about nature • Question – Why or how the event occurs • Hypothesis – Proposed or tentative answer • Experiment – Test with variable & control • Conclusion – Analyze data interpret results • Theory – Explains why, allows prediction • Natural Law – Explains how nature behaves

6. Scientific Method Flow Chart Question Observe Hypothesis Experiment Reject Accept Natural Conclusion Law Theory

7. Safety in the Laboratory • Rules & Procedures • Follow teacher’s and lab directions • Notify teacher of problems • Know how to use safety equipment • Wear safety goggles at all times • Tie back long hair • Avoid awkward transfers • Let hot stuff cool or use tongs / hot mitts • Carry chemicals defensively • Dispose of wastes properly • Clean up after lab

8. Branches of Physics • Mechanics- motion, forces, work, & power • Thermodynamics - Heat • Waves- mechanism of energy transfer • Electricity & magnetism – Forms of energy • Nuclear – composition and energy Stored in matter.

9. Measurement and Problem Solving • The Metric System • International System of units – SI • MKS system in Physics

10. Measurement Continued… • Meter – m -Base unit of length – distance that light travels in 1 299 792 458th of a second. • Kilogram – kg-Unit of mass standard is a natural object • Force and Weight- Unit is newton (N) = Kg.m/s2 • Second – s- time for 9 192 631 770 vibrations of Ce133 • Area and Volume Derived Units (combination of base units) cm2 or m2 - area cm3 or m3 - volume • 1dm3=1liter 1 cm3=1 ml • Be careful converting between units

11. Some Derived Units

12. Common Metric Prefixes

13. Uncertainty in Measurement • Making Measurements • All Measurements are uncertain • Every measurement involves estimation • This uncertainty can be expressed as ± x where x is the smallest measure possible with that instrument • Reliability in measurement • Precision - Repeatability of measurement • Accuracy - Nearness to accepted value

14. ? Precise Not Accurate Accuracy vs. Precision ? Accurate Not Precise ? Not Accurate or Precise ? Accurate And Precise

15. Working with Numbers • Significant Digits • Measurements are only as precise as the instrument • Numbers must be rounded to the correct number of significant figures • Atlantic Pacific Rule - If a decimal point is present count from the Pacific side starting with the first nonzero digit. If a decimal is absent count from the Atlantic side starting with the first nonzero digit

16. Rules for Significant Figures • All zeros between nonzero digits are significant (count) • All nonzero figures are significant. (count) • Zeros to the left of an expressed decimal and to the right of a nonzero digit are significant (count) • Zeros to the right of an expressed decimal and left of a nonzero digit are not significant (don’t count) • Zeros to the right of nonzero digits that are right of the decimal are significant (count them) • If there is no expressed decimal all zeros to the right of the last nonzero digit are not significant (don’t count)

17. Practice on Significant Figures 3000 1 3000 .00105 3 .00105 3.006 4 3.006 4020 4020 3 4020 .7000 4 .7000 80.007 5 80.007 2 .00091 .00091 2 50. 50.

18. II. Significant digits in Calculations A. When multiplying or dividing round to the least number of significant figures used in the operation Example: 2 X 12 = 24 round to 20 B. When adding and subtracting round to the fewest decimal places used Example: 3.02 + 5.3 + 1.158 = 9.478 round to 9.5 C. Conversions and exact numbers (counting numbers) have infinite significant digits Example .0432 km X 1000 m/km = 43.2 m D. If several operations are performed don’t round until the final answer E.If the last number is  5 Round up or < 5 round down III.Scientific Notation useful in working with very large or small numbers A. Make sure you can convert from and to scientific notation ( See worksheets and handout)

19. Error & Deviation IV. Percent Error- measures accuracy A. Absolute Error (Ea) B. Relative error (ER) is calculated by taking the observed value (O) minus the actual value (A) (this is absolute error (Ea)) and dividing by the actual value (A) then multiplying by 100. C. Relative error is a measure of accuracy V. Deviation – measures precision A. Absolute Deviation (Da) B. Relative Deviation (DR) is calculated by taking average of the absolute deviations and dividing by the mean (M) then multiplying by 100. C. Relative deviation is a measure of precision.

20. Scalars and Vectors • Scalar quantities have magnitude only – No Direction- can be expressed by single numbers with appropriate units Ex. Energy & Temperature • Vector quantities require magnitude and direction for their complete description. Trigonometric rules of vector addition must be followed to solve vector problems. The resultant may be calculated mathematically or measured graphically with a carefully constructed diagram.

21. Problem Solving • Use dimensional analysis (factor labeling) to solve word problems • Conversion factors should be used to cancel the units you don’t want and leave behind the units you do want • Always list the information you do know then read carefully to find out what you need to calculate. Set up the problem to solve for what you want to know. Check your answer to see if it is reasonable and in the correct units. Practice - Practice - Practice You must have this skill!

22. Pythagorean Theorem http://127.0.0.1:26300/Principles_of_Physics/01_Measurement%20and%20Mathematics/17/sp.html

23. Trigonometric Funtions  http://127.0.0.1:26300/Principles_of_Physics/01_Measurement%20and%20Mathematics/18/sp.html

24. Sample problem: trigonometry http://127.0.0.1:26300/Principles_of_Physics/01_Measurement%20and%20Mathematics/20/sp.html

25. Your Turn! http://127.0.0.1:26300/Principles_of_Physics/01_Measurement%20and%20Mathematics/21/sp.html

26. Problem Solving cont… • Graphing • Label each axis with the variable and unit and give the graph a title • Independent variable goes on the X axis Dependent variable on the Y axis • Plot data points and connect with a best fit line (not dot to dot) • Use the finished graph to establish relationships (directly proportional, inverse, logarithmic) between the variables

27. Credits • Text – Principles of Physics – Kinetic Books • Microsoft Publishing Gallary • Microsoft Equation Editor