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A Physics Toolkit

A Physics Toolkit. Chapter 1. 1.1 Physics. Energy, matter and their relationship Understanding the physical world Careers Scientists, astronomers, engineers, teachers, computer science, medicine. Mathematics. Language of physics Model observations Representations

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A Physics Toolkit

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  1. A Physics Toolkit Chapter 1

  2. 1.1 Physics • Energy, matter and their relationship • Understanding the physical world • Careers • Scientists, astronomers, engineers, teachers, computer science, medicine

  3. Mathematics • Language of physics • Model observations • Representations • Equations, pictures, force diagrams, written descriptions, motion maps…

  4. DOES IT MAKE SENSE?? • Numbers, units, blah, blah, blah • Copper ball falls 5 m. • Calculated answers: 0.002 s or 17 s

  5. SI Units • 7 base units: Meter, Kilogram, Second, Kelvin, Mole, Ampere, Candela • Everything else is derived • Joule • Coulomb • Newton

  6. Conversions • Femto (10-15) to tera (1012) • Same as chemistry • Dimensional analysis • 1kg/1000g = 1

  7. Significant Figures • Zeros to locate the decimal are not significant • Scientific notation makes it easier to identify significant zeros • Arithmetic result may never be more precise than the least precise measurement • Addition, subtraction, multiplication, division • Counting numbers are exact

  8. Scientific Methods • Make observations • Do experiments • Create models or theories to explain results • Repeat for many iterations • How are variables related?

  9. MODELS, Laws, Theories • Models based on experimentation • Atomic model, Bohr model, Quantum model • New data that doesn’t fit existing model • Evaluate both data and model • Reproducibility of data • Validity of model

  10. Models, LAWS, Theories • Rule of nature • Sums up related observations • Describes pattern in nature • Conservation laws, Law of reflection • Do NOT explain why things happen

  11. Models, Laws, THEORIES • Explanation based on many observations • Based on experimental results • May be explanations of laws • Only a well supported explanation • Theory of Universal Gravitation, Atomic Theory

  12. 1.2 Measurement • Comparison between a standard and unknown quantity • Often reported with uncertainty • If values overlap within uncertainty, data agrees • Figure 1-10, pg 12

  13. PRECISION versus Accuracy • Degree of exactness of measurement • Smallest amount of uncertainty is most precise • Depends on instrument and technique • Finest division on device • Precision is ½ smallest division • Graduated cylinder with 1 mL division • Beaker with 50 mL division • Shown by significant figures

  14. Precision versus ACCURACY • Describes how well measurements agree with the accepted value • Real value versus Accepted value • Can you ever know the exact measurement? • Yes and no

  15. Good Measurements • Read measurements at eye level • Reduces error caused by parallax • Carefully • Multiple times as necessary • Correct device for type of measurement

  16. 1.3 Graphing Data • Represent relationships between variables • Independent variable is manipulated • Dependent variable responds • Rule of One

  17. Line of Best Fit • Best model of the data • Drawn close to all data points possible • Problem-solving strategies, pg 16

  18. Linear Relationships • Dependent variable varies linearly with independent variable • Relationship is y=mx+b • Use points on the line of best fit to calculate slope and y-intercept • Slope = change in y over change in x

  19. Nonlinear Relationships • Quadratic • y = ax2 + bx + c • One variable depends on the square of another • Inverse (hyperbola) • y = a/x • One variable depends on the inverse of the other • Others

  20. Predicting Values • Can use the graph to make predictions • Interpolation • Extrapolation • Can use the equation for the graph to make predictions

  21. Lab • Graphing activity – after finishing slides • Vernier Caliper lab – after section 2 discussion

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