Unit 1 Units and Measurements Giancoli Sec 1

Unit 1 Units and Measurements Giancoli, Sec. 1 -1 1 -8 © 2006, B. J. Lieb

What is Physics ? Studies Fundamental Forces in Nature Gravity Weak Nuclear Electricity & Magnetism Strong Nuclear Studies Small and Large Systems Unit 1 - 02

Subfields of Physics ? • Includes; acoustics, astrophysics, atomic physics, cryogenics, electromagnetism, elementary particle physics, fluid dynamics, geophysics, mathematical physics, mechanics, molecular physics, nuclear physics, optics, plasma physics, quantum physics, solid state physics, statistical mechanics, thermodynamics. Medical Applications X-Ray CAT Scan Brain Sonogram MRI Unit 1 - 03

Topics Covered in PHYS 243 • Classical Mechanics • Fluids • Vibrations and Waves • Sound • Thermodynamics Unit 1 - 04

Measurement Uncertainty In lab you will have to estimate the uncertainty in any measurement. The result might be X =8. 8 cm ± 0. 1 cm Another way to show uncertainty is the number of significant figures – the number of reliably known digits, which might be two in this case. Unit 1 - 05

Significant Figures • 0. 0034 has two significant figures • 44. 58 has four • 800 has one, 8. 00 x 102 has three • Multiplication or Division: the final result should have only as many digits as the number with the least number of significant figures used in the calculation. 23. 66 x 1. 1 = 26. 03=26 (two) • Addition or Subtraction: the final result is no more accurate than the least accurate number used. 23. 5 + 43. 2 + 44 = 110. 7 = 111 Unit 1 - 06

Significant Figures in Mastering Physics • Mastering Physics (MP) is very strict and intolerant about significant. Most problems expect three significant figures. Fortunately you can answer every question 20 times. • MP advises students to carry the full precision on intermediate results until they obtain the final answer. They should apply their rounding rules only on the final answer. • When the student's answer is within tolerance of the full-precision answer, the score is not penalized, the number of wrong answers is not incremented, and the feedback reads: "Very close. Check the rounding and number of significant figures in your final answer. " • When the student's answer is further off, but still within a looser tolerance of the full-precision answer, the score is penalized, the number of wrong answers is incremented, and the feedback reads: "Not quite. Check through your calculations; you may have made a rounding error or used the wrong number of significant figures. " Unit 1 - 07

5. Units, Standards and SI System Length: 1 meter defined as the distance light travels in 1 / 299, 792, 458 of a second. Mass: 1 kilogram defined as a standard mass of a certain cylinder kept near Paris Unified Atomic Mass: 1 u defined as the 1/12 of the mass of the 12 C atom. 1 u = 1. 6605 x 10 -27 kg Time: 1 second defined by a cesium clock. Unit 1 - 08

Metric Prefixes You Must Know giga mega kilo centi G M k c 109 106 103 10 -2 milli micro nano pico femto m 10 -3 10 -6 10 -9 10 -12 10 -15 n p f Unit 1 - 9

Math Symbols You Must Know x>y x is greater than y y<x y is less than x y << x y is much less than x y is approximately equal x y is defined equal to x x change in x Unit 1 - 10

Converting Units • You are strongly urged to use the standard way of doing units conversion in physics. It reduces errors and is much easier for the grader to check. • It is based on the fact that you can multiply anything by ‘ 1’ without changing its value. Example: 1 inch = 2. 54 cm Thus Example: The area of a surface 5. 0 in by 3. 0 in is Unit 1 - 11

Order Of Magnitude Estimate • It is a good idea to do a rough estimate before doing a detailed calculation • Then when you work the problem, ask yourself if the result appears reasonable. Unit 1 - 12

Dimensions and Dimensional Analysis • In order to be correct, an answer must have the correct units. • Your solution must include units to show they work out • You can often use units to guide you to the answer. • Useful Rule: We can add or subtract quantities only if they have the same dimensions. • Example: Each term must have units of length. Unit 1 - 13

Math Review • I have created two review tutorial/quizzes in Mastering Physics: • Algebra Review – needed for Unit 2 (Chapter 2) • Trigonometry Review – needed for Unit 5 (Chapter 3) • These count the same as a homework. The deadline is extended but you need to know the material ASAP. • Appendix A has an excellent summary of the math you need for this course. You must understand all of the material in Appendix A-1, A-2, A-3, A-4 and A- 7. Unit 1 - 14

Unit 1 Appendix Photo and Clip Art Credits Some figures electronically reproduced by permission of Pearson Education, Inc. , Upper Saddle River, New Jersey Giancoli, PHYSICS, 6/E © 2004. Slide 1 -2 Photos and Clipart: Microsoft Clipart Collection, reproduced under general license for educational purposes. 1 -3 Photo and Clipart: Microsoft Clipart Collection, reproduced under general license for educational purposes. Unit 1 - 15