A physics toolkit
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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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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


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