A Physics Toolkit

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# A Physics Toolkit - PowerPoint PPT Presentation

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

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
• 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
• 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