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College Physics Chapter 1 INTRODUCTION: THE NATURE OF SCIENCE AND PHYSICS

College Physics Chapter 1 INTRODUCTION: THE NATURE OF SCIENCE AND PHYSICS PowerPoint Image Slideshow. Figure 1.3.

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College Physics Chapter 1 INTRODUCTION: THE NATURE OF SCIENCE AND PHYSICS

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  1. College Physics Chapter 1 INTRODUCTION: THE NATURE OF SCIENCE AND PHYSICS PowerPoint Image Slideshow

  2. Figure 1.3 • The Apple “iPhone” is a common smart phone with a GPS function. Physics describes the way that electricity flows through the circuits of this device. Engineers use their knowledge of physics to construct an iPhone with features that consumers will enjoy. One specific feature of an iPhone is the GPS function. GPS uses physics equations to determine the driving time between two locations on a map. (credit: @gletham GIS, Social, Mobile Tech Images)

  3. Figure 1.17 • Distances given in unknown units are maddeningly useless.

  4. Fundamental SI Units • Some physical quantities are more fundamental than others and that the most fundamental physical quantities can be defined only in terms of the procedure used to measure them. The units in which they are measured are thus called fundamental units. • The meter is defined to be the distance light travels in 1/299,792,458 of a second in a vacuum. Distance traveled is speed multiplied by time.

  5. Metric Prefixes

  6. Calculations with Measured Numbers • For multiplication and division: The result should have the same number of significant figures as the quantity having the least significant figures entering into the calculation.For example, the area of a circle can be calculated from its radius using A = πr2 . Let us see how many significant figures the area has if the radius has only two—say, r = 1.2 m. (A=4.5 m2) • For addition and subtraction: The answer can contain no more decimal places than the least precise measurement.For example, 7.56 – 6.052 + 13.7 = 15.2 because the least precise number (13.7) has only one decimal place.

  7. Uncertainty • See the Physics Lab Skills Handbook, pages 3 to 24. • For calculations with uncertainties, see • the Max-Min Method (summarized on p. 14) and • Rules for the Addition of Uncertainties (summarized on p. 20). • For simple calculations, you should use the Rules for the Addition of Uncertainties. For very complex calculations, especially those involving multiple powers or trigonometric functions, it is acceptable (and easier) to use the Max-Min Method. • For another take on it, see section 1.3 in the Openstax College Physics textbook: http://cnx.org/content/m42120/latest/?collection=col11406/1.7

  8. Unit Conversions This is equal to 1, so we can multiplywithout changing the physical quantity. • Conversion factor: ratio expressing how many of one unit are equal to another unit. • E.g. 1 minute = 60 seconds • Arrange the conversion factors so you’re multiplying by 1 • E.g. • Set it up so the unwanted units cancel out, and you’re left only with the desired units. • Doing math with units is called Dimensional Analysis. It is commonly used to double-check engineering calculations. I once had a student who claimed to have earned over 80% in physics NYC simply by ensuring the units worked out in his equations!

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