1. Physics Chapter 1 Saul Beltran Mr. Kim 12/9/05 Per. 7

2. A Summary Physics, like other sciences, is a creative endeavor. It is not simply a collection of facts. Important theories are created with the idea of explaining observations. To be accepted, theories are tested by comparing their predictions with the results of actual experiments.

3. Models and Theories Scientists often devise models of physical phenomena. A model is a kind of picture or analogy that seems to explain the phenomena. A theory is usually deeper and more complex that a simple model. A scientific law is a concise statement, often expressed in the form of an equation, which quantitatively describes a particular range of phenomena over a wide range of cases.

4. Measurements and Units Measurements play a crucial role in physics, but can never be perfectly precise. It is important to specify the uncertainty of a measure either by stating it directly using the ± notation, and/or by keeping only the correct number of significant figures. The number of reliably known digits in a number is called the number of significant figures. (Example: 202 has three significant figures, but 200 only has one significant figures. Reason: when the zero is in between two numbers it is important, otherwise it is not. )

5. Measures and Unites Continued Physical quantities are always specified relative to a particular standard or unit. The unit used should always be stated. The commonly accepted set of units today is the System International (SI), in which the standard units of length, mass, and time are meter, kilogram, and second When converting units, check all conversion factors for correct cancellation of units. Making rough, order-of-magnitude estimates is a very useful technique in science as well as in everyday life.

6. Important Information Length (or distance) Meters (approximate) Neutron or proton (radius) 10٨(-15) m Atom10٨(-10) m Virus10٨(-7) m Sheet of paper10٨ (-4) m Finger width10٨(-2) m Football field length10٨(2) m Mt. Everest height10٨4 m Earth diameter10٨7 m Earth to Sun10٨11m Nearest star, distance 10٨16 m Nearest Galaxy10٨22 m Farthest Galaxy visible 10٨26 m

7. Some Typical Time Intervals and Masses Time IntervalSeconds Lifetime of very unstable particle 10٨23s Lifetime of radioactive elements 10٨22s to 10٨28s Lifetime of muon10٨-6s Time between human heartbeats 10٨0s One day10٨5s One year3x10٨7s Human life span2x10٨9s Length of recorded history 10٨11s Humans on Earth10٨14s Life on Earth10٨17s Age of Universe10٨18s ObjectKilogram Electron10٨-30 kg Proton, neutron10 ٨-27 kg DNA molecule10 ٨-17 kg Bacterium10 ٨-15 kg Mosquito10 ٨-5 kg Plum10 ٨-1kg Person10 ٨2 kg Ship10 ٨8 kg Earth6x10 ٨24kg Sun2x10 ٨30 kg Galaxy10 ٨41 kg

8. Metric (SI) Prefixes PrefixAbbreviationValue ExaE10 ٨18 PetaP10 ٨15 TeraT10 ٨12 GigaG10 ٨9 MegaM10 ٨6 KiloK10 ٨3 HectoH10 ٨2 DecaDa10 ٨1 DeciD10 ٨-1 CentiC10 ٨-2 MilliM10 ٨-3 Microu10 ٨-6 NanoN10 ٨-9 PicoP10 ٨-12 FemtoF10 ٨ -15 AttoA10 ٨-18

9. The End? Thank you for listing to this presentation. If you are still reading this, then you have too much time because you are interested in physics. Now get ready for the test suckers.

10. Quiz http://www.homework55.com/physics/ph8- 16-05/Significant%20Figures.htm