**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 • Equations, pictures, force diagrams, written descriptions, motion maps…

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

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

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

**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

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

**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

**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

**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

**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

**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

**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

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

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

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

**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

**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

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

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