Chapter 1: Introduction and Measurement

Transcription

1 Chapter 1: Introduction and Measurement Brent Royuk Phys-111 Concordia University Learning in a Christian Context What does it mean that Concordia is a Christian school and how does that affect us in this class? 1. We know that science is not the most important thing in the world. 2. We are in a Christian learning community and trust each other as brothers and sisters in Christ. 3. We acknowledge scholarship as an important activity for Christians to pursue. For a Christian, the mind is important because God is important. -Mark A. Knoll 4. We enjoy and appreciate learning about the natural world because we know who created it. We marvel at the scientific order and complexity of the universe and seek knowledge with a worshipful attitude. 5. We recognize that God has called us to our current vocation. At this point in our lives, we have not only chosen to be a student- we have answered God s call for us to accomplish his work on earth as a student. 6. So whether you eat or drink or whatever you do, do it all for the glory of God. 1 Cor. :31 2 Find the slope of this line: Given: a = 2, b =3, c =4. Find d. 2a 2 b = d c a = b2 cd Given each of the following equations, solve for n: For the following triangle find the length of side AB and the measure of angle C. ω 2 = 2nθ b 3 = 5n F = G m m 1 2 a 2 n 2 Solve for n in terms of b: 3n = 2a+ b 2n = 2a 4b 5 6 1

2 Foundations of Physics Before we consider what physics is, let s consider science in general. How would you answer the question What is science? The Scientific Method 1. Define the question 2. Gather information and resources 3. Form a hypothesis 4. Perform an experiment and collect data 5. Analyze data 6. Interpret data and draw conclusions that serve as a starting point for new hypotheses 7. Publish results 7 8 Problems with the Scientific Method Too procedural There really isn t a scientific method. the only principle that does not inhibit progress is: anything goes. --Paul Feyerabend Deductive (general to specific) instead of inductive (specific to general) Individual experiments tend to be deductive, but a broad picture of the history and NOS is inductive. From Gil Daenzer 1. Observe Nature (Facts) 2. Find Order (Laws) 3. Build Models (Theories) 4. Explain & Predict This is a conceptual model for science, rather than a procedural one. 9 Example 1. I saw a sunrise today (Fact) 2. The sun rises in the east (Law) 3. What s the theory? Example 1. Drop a rock: it falls (Fact) 2. Things fall (Law) 3. What s the theory?

3 Scientific Laws An observed regularity Laws are simple. Scientific laws are descriptive, not prescriptive. Scientific laws are discovered, not invented. God makes laws, not man. 13 Some Scientific Laws Boyle s Law Charles Law Newton s Laws of Motion Kepler s Laws of Planetary Motion Coulomb s Law Hubble s Law Ohm s Law Maxwell s Equations Snell s Law The Laws of Thermodynamics The Law of Definite Composition The Law of Conservation of Mass/Energy Buys-Ballot's law (wind travels counterclockwise around low pressure systems in the Northern Hemisphere) Geology: The law of stratigraphic succession 14 Some More Laws Macfarlane's Law You can talk faster than you can type, but you can read faster than you can listen. Godwin's Law An adage in Internet culture that states As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one. Dilbert s Law the most ineffective workers are systematically moved to the place where they can do the least damage: management. Scientific Theories A scientific theory is a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses. -- National Academy of s Theories are the conceptual product of science God doesn t make scientific theories, we do. One-word synonyms: Model, framework, explanation Some Well-Known Scientific Theories Problems with the Scientific Method: The Grade-School Scientific Certainty Myth Relativity Theory Atomic-Molecular Theory Kinetic Theory Quantum Theory String Theory Grand Unification Theory Germ Theory of Disease Plate Tectonics Evolutionary Theory Evolutionary Psychology Wrong: 1. Hypothesis 2. Theory 3. Law So a Law is a proven theory! Better: 1. Law 2. Theory 3. Hypothesis A theory is never proven

4 What is Physics? Old science Natural Philosophy The Queen of the s Physics envy All science is either physics or stamp collecting. Ernest Rutherford... it is impossible to explain honestly the beauties of the laws of nature in away that people can feel, without their having some deep understanding of mathematics. I am sorry, but this seems to be the case. Richard Feynman Standardization is necessary for science (the king s thumb) Cubits, Thumb = inch, 12 inches = foot, three feet = yard 1793, French Academy of s 1983: The distance light travels in 1/299,792,458 second The kilogram One cubic tenth of a meter of water The gram/milliliter/cc connection Prototype Pt-Ir cylinder Where did the second come from? 1 sec = 9,192,631,770 oscillations of Cs-133 radiation The speed of time is one second per second. The MKS system vs. cgs, fps The liter The seven base units Prefix Symbol Magnitude Meaning (multiply by) Yotta- Y Zetta- Z Exa- E Peta- P Tera- T Giga- G Mega- M myria- my (this is now obsolete) kilo- k 3 00 hecto- h 2 0 deka- da deci- d centi- c milli- m micro- u (mu) nano- n pico- p femto- f atto- a zepto- z yocto- y

5 Try these: 3.4 cm = m ng = kg 340 g = kg 3.4 x -11 km = mm Dimensional Analysis Derived units can have funny dimensions e.g. 1 J=1 kgm 2 /s 2 Sometimes you can decide if an equation is false if it doesn t work out dimensionally e.g. v = 2ax Do math with units: m s = 2 m s 2 m You might also see [a] = m/s 2 We will do math with units just like with numbers Example: Use v=p/m to find v given p =12 kg m/s and m = 4.0 kg Converting Units These are all velocity units: m/s, ft/s, mph, cm/min, cubits/week, attoparsecs/ microfortnight All can be used interchangeably The conversion factor method: 12 ft = yd 34 km/h = m/s 18 kg/m 3 = slugs/ft 3 1 mph = km/min At desk: 1 mile/(min) 2 = m/s 2 1 apc/ fortnight = cm/s Fermi: 1 microcentury equals about one lecture period Problem Solving Problem Solving Do it for you, not for me. For problem solving, we will use: Good Form: 1. Identify Given/Need. 2. Write the equation to be used. 3. Algebraically solve for the desired quantity. 4. Substitute in known values. 5. Write your answer with units & proper sig-figs. 32 5