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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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