Unit 0: Orientation to Class The Structure of Physics McCaskie, Room 210 2017 – 2018

What is Physics?!? PHYSICS: The branch of science that involves the study of the Physical world What is “The Physical World?”

Physics deals with 3 things Energy Forces Motion KNOW THIS!

First Thing is first – the scientific method Make an observation Research/gather information Form a hypothesis Test the hypothesis (i.e. experiment) Analyze data Draw conclusions Peer review

Which is the best way to approach a hypothesis? What is a hypothesis? Hypothesis Which is the best way to approach a hypothesis? Possible explanation based on what is already known Based on observations  Leads to a model  Dictates experimentation Objective – not influenced by personal feelings Subjective – influenced by personal feelings, tastes or opinions

What is a model? A representation of an idea, event, structure, or object that helps people understand it better

Modern computer models

Scientific Theory or Scientific Law Explanation of things or events based on knowledge gained from observations or investigations “You know what? I think…” Statement about what happens in nature and seems to be true all the time Based on countless “proven” theories For Instance, Gravity

Science has limitations It cannot explain everything! It is a procedure that either “proves or disproves” a guess Must be tested What is the problem with that? It is rooted in objectivity

The fun part… GET READY… IT’S COMING…

WHY the H*** do we need math in physics?! Equations show relationships between measurements Theories  experiments  numerical results  analysis  models that can be used to investigate similar observations

International system of Units (SI) Base Units KNOW THESE!!! Length = meter (m) Mass = kilogram (KG) Time = second (s) Temperature = Kelvin (K) Amount of a substance = mole (mol) Electric current = ampere (A) Luminous intensity = candela (cd)

SI Unit conversions

Practice… How many centigrams are in 100 grams? How many megagrams are in 4 milligrams? How many nanograms are in a hectogram? How many grams are in 64.79 micrograms?

Dimensional analysis

Dimensional analysis A relationship between all units and dimensional analysis is a way to surf between those units For instance, how many cars are in a week? …yes you can! A method of treating units as algebraic quantities that can be cancelled in order to predetermine if your physics equations are set up properly

Dimensional analysis practice How many feet tall is a peak that is 8000 meters tall? If an apartment has an area of 880 square feet, how many meters is that? A posted speed limit sign state the speed limit is 55 miles per hour. How fast is that in meters per second? In kilometers per hour?

Break time?

Significant figures Definition – valid digits in a measurement Measurement is inherently flawed, based on user error, and imprecise tools Therefore, number of significant figures is determined by how precise the measurement is is your pen 138 mm? 138.1 mm? 138.10 mm? 138.15 mm?

Rules for significant figures Nonzero digits are always significant 37 = 2 sig figs Any zero between 2 nonzero digits are significant 407 = 3 sig figs Final zeros to the right of a decimal point are significant 37.0 = 3 sig figs Zeros to the left of a decimal point/Space holding zeros are NOT significant 4500 = 45 X 102 = 2 sig figs YEP! KNOW THIS TOO!!!!

Measurement

Measurement = comparison between an unknown quantity and a standard Mass of a shopping cart Blood pressure Height weight Gram (g) Range between 110/60 – 130/90 mmHg Meters (m) Gram (g)/ kilogram (kg)

Precise vs. accurate Precision Accuracy How well the measurements “agree” with the real value How close are all measurements to each other Degree of exactness “how close to the bullseye?”

Graphing Data

First Identify variables Independent variable – the factor that is being manipulated Ex.: masses of different object hanging from different springs Dependent variable – the factor that depends on the independent Variable Ex.: springs stretching in response to masses

Create a graph X- and y- axes Shows the relationship between independent and dependent variables

Example of constructing a graph Mass attached to spring Length of spring 13.7 5 14.1 10 14.5 15 14.9 20 15.3 25 15.7 30 16.0 35 16.4

Practice time

Types of graphical relationships Linear Nonlinear Dependent variable varies linearly with independent variable Y = mx + B Dependent variable varies in a non- linear fashion with independent variable Quadratic functions Inverse relationships

Nonlinear relationships Quadratic Relationship Inverse relationship