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08/18/10 - Chapter 1 - Introduction
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 | 1.1 The Purpose of Physics
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 | Discovering patterns in how the physical world works.
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| Creating models so that we can predict the behavior of natural processes.
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| Before Galileo (1564-1642), people generally trusted authoritarian experts such as Aristotle, rather than trust their own experience. Aristotle explained motion by talking about earth, water, air, fire and aether. A rock sank in water because it contained earth and naturally wanted to "seek its level." Wood floats in water because it contains some air which causes it to rise to its natural level (above water) but it also contained some earth, so it's heavier than pure air and rests at the bottom of the air-water interface. Etc.
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| Galileo said you don't need to accept "expert" opinion, just ask Mother Nature (i.e., do the experiment yourself and see what happens).
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| A sense of wonder - Einstein sayings:
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| Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
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| He who can no longer pause to wonder and stand rapt in awe, is as good as dead; his eyes are closed.
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| It is a miracle that curiosity survives formal education.
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| Joy in looking and comprehending is nature's most beautiful gift.
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| The most incomprehensible thing about the world is that it is comprehensible.
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| The most beautiful thing we can experience is the mysterious. It is the source of all true art and science.
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| The only reason for time is so that everything doesn't happen at once.
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| The only thing that interferes with my learning is my education.
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| The whole of science is nothing more than a refinement of everyday thinking.
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| There are two ways to live: you can live as if nothing is a miracle; you can live as if everything is a miracle.
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| We still do not know one thousandth of one percent of what nature has revealed to us.
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| When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity.
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| Liberal education - broad background and seeing connections
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| Responsible Citizenship - climate change, alternative energy, ...
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| Learn how nature works so that we can work with it.
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| Build bridges to cross rivers or canyons.
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| Engineering is applied physics.
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| 1.2 Problem Solving in Physics: Reasoning and Relationships
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| Using the relationships between nature's laws, we can anticipate how changes in one system will produce changes in another system.
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| Scientific Notation and Significant Figures
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| 299,790,000 = 2.9979 x 108 has 5 significant figures (2.9979)
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| 0.00000000000000000016 = 1.6 x 10-19 has 2 significant figures (1.6)
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| 500 = 5 x 102 has 1 significant figure (5).
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| 500. = 5.00 x 102 has 3 significant figures (5.00).
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| Rule for significant figures in calculations involving addition and subtraction
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| The location of the least significant digit in the answer is determined by the location of the least significant digit in the starting quantity that is known with the least accuracy.
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| 4.52 + 1.2 = 5.72 rounded to one decimal place: 5.7
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| 4.52 - 4.1 = 0.42 rounded to one decimal place: 0.4
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| Rule for significant figures in calculations involving multiplication and division
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| Use the full accuracy of all known quantities when doing the computation. At the end of the calculation, round the answer to the number of significant figures present in the least precise starting quantity.
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| 12 x 0.062 = 0.744 rounded to 0.74
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| 12 x 0.062464 = 0.749568 rounded to 0.75
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| 1.4 Physical Quantities and Units of Measure
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| Need to be quantitative to determine relative importance of different effects.
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| Importance of measurements
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| Usually involves fractions (3/64-inch) or historic relationships (16 ounces to a pound, 12 inches to a foot, 1760 yards to a mile, ...)
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| Prefixes based on powers of 10: mega = 1000000 = 106, kilo = 1000 = 103, centi = 1/100 = 10-2, milli = 1/1000 = 10-3, micro = 1/1000000 = 10-6, ...
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| SI (international system) used to be called MKS (meters-kilograms-seconds) System
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| Changing inches to meters:
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| Changing pounds to kilograms:
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| 1.6 Algebra and Systems of Equations
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| Solve the following equation for dO:
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| Solve the following system of equations for a and b:
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| Ratios of sides of right triangles
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| Displacement is a vector which indicates a change in position.
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| For example, if an object moved from a point 1 meter to the right of a reference point on the whiteboard to a point 3 meters to the right of the reference point, we would say its displacement was 2 meters. Since displacement is defined as the final position minus the initial position, we find the displacement by taking the final position (3 meters) and subtracting the initial position (1 meter), which gives us 2 meters. Symbolically, we write displacement ∆x = 3 - 1 = 2 meters. The ∆ is the Greek letter delta and means "change in". So ∆x means "change in x".
If it moved from the same starting point to a point 3 meters to the left of the reference point, we would say its displacement was -4 meters.
For motion in one dimension, direction is indicated by the sign of the number: + or -.
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| In two dimensions, objects can move in both the horizontal (x) and vertical (y) direction at the same time. The horizontal (x) direction is indicated by the unit vector i, and the vertical (y) direction is indicated by the unit vector j. A unit vector has a length of 1 and just indicates a direction. The displacement shown below from (x, y) = (0.5, 0.5) to (x, y) = (5.5, 3.5) is ∆d = (5.5 - 0.5)i + (3.5 - 0.5)j = 5i + 3j. Notice we can't combine the 5i + 3j to get 8 anything because the 5 and the 3 are in different directions.
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| In three dimensions, objects can move in the horizontal (x), vertical (y) and depth (z) direction at the same time. The figure below shows the vector 5i + 3j + 2k (green) and its (x, y, z) components (5i purple, 3j red, 2k blue).
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| Vectors can be discribed by magnitude and direction
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| The magnitude of a vector can be found from the Pythagorean Theorem
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The magnitude (length) of the green vector is the length of the hypotenuse:
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| The magnitude of the vector 5i + 3j + 2k is
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| Add the tail of one vector to the tip of the other. Order does not matter. The resultant goes from the tail of the first vector to the tip of the last vector.
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 | Addition of vectors adding corresponding components
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| (7i + 2j - 3k) + (2i + 5j + 4k) = 9i + 7j + k
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| Multiplying a vector by a number
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| changes its length (and reverses its direction if the number is negative)
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| 4(7i + 2j - 3k) = 28i + 8j - 12k
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| Multiply the vector being subtracted by -1 to reverse its direction and add it to the other vector.
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| (7i + 2j - 3k) - (2i + 5j + 4k) = (7i + 2j - 3k) + (-2i - 5j - 4k) = 5i -3j - 7k
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| Multiply vector A by 2 to double its length and add 3 times vector B and reverse the direction of vector C, increase its length by a factor of 5 and add it to the previous result.
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| 2(3i - 4j + k) + 3(i + 2j - 5k) - 5(-2i + 3j + 4k) = (6i - 8j + 2k) + (3i + 6j - 10k) + (10i - 15j - 20k) = 19i - 17j - 28k
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| Purchase the textbook and read Section 1.1-1.7.
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| Class key for WebAssign: canadacollege 3547 0686
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| WebAssign Student Quick-Start Guide (double-click on the page below to see the whole document)
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| Read the article by Nobel Prize winner Richard Feynman, "What is Science?" (http://www.civerson.com/P210/WhatIsScience.pdf). Pick out five statements he makes and write about them, comparing or contrasting your thoughts to his. Provide your own examples which illustrate his points or contradict them. Send your work to me pasted into an email or as an email attachment: iverson@smccd.edu. The subject of your email should read: P210 - What is Science?
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