PSSA PREP: Compared to the charge and mass of a proton, an electron has: A. the same charge and a smaller mass B. the same charge and the same mass C.

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PSSA PREP: Compared to the charge and mass of a proton, an electron has: A. the same charge and a smaller mass B. the same charge and the same mass C. an opposite charge and a smaller mass D. an opposite charge and the same mass Slide 2 UNITS AND CONVERSIONS Slide 3 What will be covered: SI Units Metric Prefixes and Order of Magnitude Factor-label conversions Multi-dimensional conversions How will it be tested: The contents of this section will be embedded in EVERYTHING we do this year. I will always take off points for incorrect or lack of units and poor conversions. It is very important that we get these skills down right away, as they will erode our grades if we dont. Slide 4 SI Units International System of Units SI (French: Le Systme international d'units) The modern form of the metric system. SI is NOT a static set of units The United States and the United Kingdom are pretty much the only two countries that do not wholly and singly acknowledge this system. Slide 5 SI Units : Length The Meter (m) Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent 1/10,000,000 of the distance from the equator to the north pole through Paris.French Academy of Sciences Today, it is defined by the International Bureau of Weights and Measures as the distance travelled by light in absolute vacuum in 1/299,792,458 of a second.International Bureau of Weights and Measureslightvacuumsecond Slide 6 SI Units:Mass The Kilogram (kg) It is defined as being equal to the mass of the International Prototype Kilogram. It is the only SI base unit with an SI prefix as part of its name.SI prefix It is also the only SI unit that is still defined in relation to an artifact rather than to a fundamental physical property that can be reproduced in different laboratories.artifact The mass of the kilogram is almost exactly equal to that of one liter of water.liter Slide 7 SI Units: Time The Second (s) The second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom at absolute zero.periodshyperfine levels ground statecaesiumatom Slide 8 SI Units: Temperature The Kelvin (K) The definition of the kelvin has three parts: It fixes the magnitude of the kelvin unit as being precisely 1 part in 273.16 parts the difference between absolute zero and the triple point of water; It establishes that one kelvin has precisely the same magnitude as a one-degree increment on the Celsius scale; and It establishes the difference between the two scales null points as being precisely 273.15 kelvins (0 K = 273.15 C and 273.16 K = 0.01 C). Slide 9 SI Units: Others SI units also exist for: electric current the amount of a substance luminous intensity ***These units will be introduced as we encounter the topics throughout this course. Slide 10 PSSA Prep: Two streams begin at the same elevation and have equal volumes. Which statement best explains why one stream could be flowing faster than the other stream? A. The faster stream contains more dissolved minerals. B. The faster stream has a much steeper gradient. C. The streams are flowing in different directions. D. The faster stream has a temperature of 10C, and the slower stream has a temperature of 20C. Slide 11 Scientific Notation In scientific notation, all numbers are written in the form: A x 10 B C - Where A is a real number between 1 and 10 -Where B is an integer - Where C is the unit of measurement Slide 12 Scientific Notation A x 10 B -The notation x 10 B can be interpreted as multiply A by ten B times Example: 3.5 x 10 4 m = 3.5 x 10 x 10 x 10 x 10 m = 35,000 m -When B is negative, it should be interpreted as multiply A by one-tenth B times Example: Slide 13 Scientific Notation Practice: Put these numbers into scientific notation: 49,000 m.00598 Kg 36,000,000 s Slide 14 Significant Digits -Significant Digits are the digits in a measurement that are reliable. Identifying Significant Digits: 1. Nonzero digits are always significant. 2. All final zeros after the decimal point are significant. 3. Zeros between two other significant digits are always significant. 4. Zeros used solely as placeholders are not significant. Slide 15 Significant Digits How many significant digits does each number have? A.) 15.45 m B.) 306.29 kg C.) 0.00436 L D.) 34.07900 J E.) 8.51 x 10 6 m The Rules: 1. Nonzero digits are always significant. 2.All final zeros after the decimal point are significant. 3. Zeros between two other significant digits are always significant. 4. Zeros used solely as placeholders are not significant. Slide 16 Significant Digits -These digits affect whether or not certain calculations make sense to perform. Example: A man is measuring a hallway in which he plans to install carpet. He measures the hallway and records it to be 12 m long. When his wife gets home, she asks if he remembered that the carpet must go under the baseboards. He truthfully states that he didnt. Should he add the extra 0.08 meters to his measurement? Why or why not? Slide 17 Significant Digits Addition and Subtraction: Find the least precise measurement, perform the operation, and round the answer to the same place as the least precise significant figure. Example: Add 6.789 m + 43.5 m + 18 m 6.789 m 43.9 m +18. m 68.689 m = 69 m Slide 18 Significant Digits Multiplication and Division: Perform the operation, then count the significant figures of the factor with the fewest sig. figs. Round your final answer so that it has the same number of sig. figs. Example: Divide: 205 m /.347 s / 5 s 3 sig. fig. 1 sig. fig. = ? Slide 19 SI Prefixes http://en.wikipedia.org/wiki/SI_prefix The metric prefix is used to allow measurements to become decimal-multiples that fall between.1 and 1000. Slide 20 SI Prefixes The SI prefix takes the place of the order of magnitude multiple when a measurement is written in scientific notation: 8,000,000 m = 8.0 x10 6 m = 8.0 Mm Slide 21 Orders of Magnitude A way of comparing relative changes in measurements. When something is about 10x bigger than another, we say that it is one order of magnitude larger than the other. A scientist leaves 30 bacteria in a dish over night. When he returns 12 hours later, he sees that there are now 400. He accurately states that in 12 hours, the bacteria has increased its population by an order of magnitude. Slide 22 Orders of Magnitude Simpsons Power of Ten movie from Introduction Media Files Slide 23 Order of magnitude Orders of Magnitude can be used to make vague estimates for numbers that would be very difficult to find... These estimates are often called Fermi Estimations When checking ones solution to a problem, or wondering whether or not a measurement was taken correctly, it is wise to check if the answer is on the correct order of magnitude Slide 24 Orders of Magnitude ~ 1 byte (1 note of a song) Slide 25 Orders of Magnitude ~ 800 Hectobytes (A Nintendo song) Slide 26 Orders of Magnitude ~ 1400 kilobytes (one low quality mp3) Slide 27 Orders of Magnitude ~100 Megabytes (One Medium Quality.mp3 Album or 1 High quality.wav file) Slide 28 Orders of Magnitude ~1 gigabyte (10.mp3 albums or 1 high quality.wav album) Slide 29 Orders of Magnitude ~1 terabyte (100,000 high quality.mp3 songs, or 1 music store of high quality.wav files) Slide 30 Resources http://en.wikipedia.org/wiki/siunits Time Service Department, United States Naval ObservatoryUnited States Naval Observatory