Physics Chapter 1, The Science of Physics From: Holt Physics, 2006
Areas within Physics • *Mechanics: Studies motion and interactions between objects. • Examples: Falling objects, friction, weight, spinning objects.
*Thermodynamics • *Studies heat and temperature. • Examples: melting and freezing processes, engines, refrigerators.
*Vibrations and Waves • *Deals with repetitive motions. • Examples: Springs, pendulums, sound
*Optics • *Studies Light • Examples: Mirrors, lenses, color, astronomy
*Electromagnetism • *Deals with electricity, magnetism, and light • Examples: Circuits, electronics
*Relativity • *Studies particles that are moving at any speed, even very high speeds • Examples: traveling at high speeds, particle accelerators, particle collisions.
*Quantum Mechanics • *Studies the behavior of submicroscopic particles. • Examples: The atom and its parts
Scientists use the Scientific Method to investigate things. • 1. Make observations and collect data that lead to a question. • 2. Make a hypothesis • 3. Test Hypotheses by using experiments. • 4. Interpret results, and revise the hypothesis if necessary. • 5. Make conclusions. • *A Hypothesis is an explanation you make to account for your observations.
Models are simplified representations that are used to explain complex things. • Many times a model is a diagram or a computer simulation.
A good physics model can predict what will happen in new situations. • If a model does not correctly predict what will happen, it needs to be changed.
A System is the specific things you want to study. For example, studying the circuitry of a TI-82 Calculator.
A controlled experiment tests one factor at a time. • Controls are held constant in the experiment.
Create a fair race to see which animal, on average, is faster over 100 m
See which type of barbeque sauce people in America like better: • Sweet and Tangy: Hot and Spicy: BBQ BBQ
Section 2, Measurements in Experiments • Dimension describes the kind of physical quantity you are measuring. • Three basic dimensions are length, mass, and time. • These three are used in different combinations to describe many things like force, velocity, energy, etc.
How much of something you have is given by Units. Like centimeters, kilometers, etc. • SI is the standard measurement system for science. • Each unit is defined by a standard, for example, a “Meter is officially the distance light travels, in a vacuum, in 1/299,792,458 seconds with time measured by a cesium-133 atomic clock which emits pulses of radiation at very rapid, regular intervals.” from: http://www.surveyhistory.org/the_standard_meter1.htm
Prefixes can be used in front of units to mean powers of 10. • Micro = 10-6, like a micrometer. This means that there are 10-6 meters in a micrometer. • Kilo = 103, This means that there are 103 meters in a kilometer.
Scientific Notation • 1,400,000 = 1.4 x 106 • .00056 = 5.6 x 10 —4
Units Conversion: • Use Conversion Factors to convert from one unit to another. • Conversion Factors are always equal to 1. Like: 1 mm / 10-3 m = 1. Or 106 m / 1 Megameter = 1. See Table 3 in book.
Example, convert 7 mm to m. Example 2: Convert 12.4 megameters to centimeters.
Convert 4 m3 to cm3: • Convert 6,000 m3 to km3 • Convert 7 km/s2 to m/s2
*Accuracy and Precision • *Accuracy: How close a measurement comes to the correct value. • *Precision: How close a series of measurements are to one another. Or, how exact a measurement can get, based on the instrument you are using.
Method error = An error caused by taking some measurements with one process, and using a different process to take other measurements. • Instrument error Errors caused by faulty equipment.
Determining Error of a measurement • Error = [Experimental Value - Accepted Value] • Percent Error = error / accepted value * 100% • Example, you measured 120 cm, but it is 130 cm.
Significant Figures: The digits in a measurement that are known with certainty, plus one digit that is estimated.
Is a Zero a Significant Number or Not? • Table 4 in book. • 504 • .006 • 50.0 • 7,000
Sig Figs in Calculations: • Addition or subraction Round the final answer to the last “shared column”. • 13.4 + 5.234
Sig Figs in Calculations: • Multiplication or Division The final answer should have the same number of sig figs as the measurement that had the least # of sig figs. • 1.50 x 2.0
Infinite Sig Figs • Exact Quantities have an infinite number of sig figs. • Like: I am holding 4 paperclips • Or: There are 12 inches in a foot
In this class, delay rounding until the very end. • (3.449 + 6.57) * 8.779 / 5.2
Physics Equations describe relationships. • V = d/t • F = m * a
Symbols in equations: Delta, Sigma • Notice how variables are bold or italicized. • Table 8 F = m * a • Units are not italicized.
On the Test: (What do the graphs look like?) • Y = mx + b • Y = 2x + b • Y = x + 3
On the Test: (What do the graphs look like?) • Y = x^2 • Y = x^2 + 1 • Y = 3x^2