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Chapter 1 Introduction © 2006, B.J. Lieb Giancoli, PHYSICS,6/E © 2004. Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey Ch 1 1 What is Physics ? •Discipline of Science dealing with the properties of matter and energy. •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. Ch 1 2 Topics Covered in PHYS 243 • Classical Mechanics •Fluids •Vibrations and Waves •Sound •Thermodynamics Ch 1 3 Measurement Uncertainty In lab you will have to estimate the uncertainty in any measurement. The result might be X =8.8 cm ± 0.1cm Ch 1 Another way to show uncertainty is the number of significant figures – the number of reliably known digits, which might be two in this case. 4 Significant Figures • 0.0034 has two significant figures • 44.58 has four • 800 has one (probably) 8.00x102 has three • the final result of multiplication or division 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 ) • the final result of addition or subtraction is no more accurate than the least accurate number used. 23.5 + 43.2 + 44 = 111 Ch 1 5 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 12C atom. 1u = 1.6605 x 10-27 kg Time: 1 second defined by a cesium clock. Ch 1 6 Metric Prefixes You must know Ch 1 giga mega kilo G M k 109 106 103 centi milli micro nano c m n 10-2 10-3 10-6 10-9 pico femto p f 10-12 10-15 7 Math Symbols x>y x is greater than y y<x y is less than x y << x y is much less than x yx y is approximately equal x yx y is defined equal to x x change in x 5 x i 1 Ch 1 i x1 x2 x3 x4 x5 8 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 any thing by ‘1’ without changing its value. Example: 1 inch = 2.54 cm Thus 1 2.54 cm 1 in 1 in 2.54 cm Example: The area of a surface 5.0 in by 3.0 in is Area (5.0 in ) ( 3.0 in ) 2 2.54 cm 2 Area (5.0 in) (3.0 in) 97 cm 1 in Ch 1 9 Order Of Magnitude Estimate • It is a good idea to do a rough estimate before doing a detailed calculation •When you work a problem, ask yourself if the result appears reasonable. Ch 1 10 Dimensions and Dimensional Analysis • In order to be correct, an answer must have the correct units. •Your solution must include units to show how 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: Ch 1 Each term has units of length. 11