Chabot Mathematics Units & Conversions Bruce Mayer, PE Licensed Electrical & Mechanical Engineer BMayer@ChabotCollege.edu Chabot College Mathematics 1 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Units Introduction People measure quantities through comparisons with standards. Every measured quantity has an associated “unit” Which is the name of the Standard. Need to define sensible and practical "units" and "standards" that scientists & engineers everywhere can agree upon Even though there exist an almost infinite number of different physical quantities, we need no more than a handful of “base” standards. Chabot College Mathematics 2 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx SI System of Units Système International d'Unités (International System of Units) A Completely Consistent Set of Basic Units • Requires NO Conversion factors – e.g., 5280 ft = 1 mile • Defined by UNCHANGING Physical Phenomena – Except for one... Chabot College Mathematics 3 http://www.bipm.org/en/si/ Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx SI System History In 1960 The 11th General Conference on Weights and Measures (GCWM) adopted the name SI System, for the recommended practical system of units of measurement. The 1960 GCWM Specified Seven well-defined “Base” units which, by convention, are regarded as DIMENSIONALLY INDEPENDENT http://www.bipm.org/en/si/ Chabot College Mathematics 4 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx ¿¿ Reader Question ?? Have you Heard of the unit: 1. METER (m) 2. KILOGRAM (kg) 3. SECOND (s) 4. AMPERE or AMP (A) 5. KELVIN (K) 6. MOLE (mol) 7. CANDELA (cd Chabot College Mathematics 5 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx From this List Observe SI Base Units SI Base Units Base quantity length mass Name Symbol meter m kilogram kg time second s electric current ampere A thermodynamic temperature kelvin K amount of substance mole mol candela cd luminous intensity All but the kg are defined by Physical Phenomena • Examine the Defs Chabot College Mathematics 6 • Very common Units – Mass (kg) – Length (m) – Time (s) • Some Not so Common Units – Current (A) – Temperature (K) • Some Uncommon Units – Substance amt (mol) – Luminous Int (cd) Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Meter Defined Length or Distance (meter) “The path traveled by light in vacuum during a time interval of 1/299792458 of a second.” 1 meter Laser photon Chabot College Mathematics 7 1/299792458 s Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx kilogram Defined Mass (kilogram) a cylinder of PLATINUMIRIDIUM alloy maintained under vacuum conditions by the International Bureau of Weights and Measures in Paris If The ProtoType Were Cubic, its Edge Length would be About 36.2 mm (1.42”); quite small Chabot College Mathematics 8 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Second Defined Time (Second) 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 cesium 133 atom • This is the Definition of an “Atomic” Clock – more than 200 atomic clocks are located in metrology institutes and observatories in more than 30 countries around the world Chabot College Mathematics 9 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Amp Defined Electric Current (ampere) That constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 m apart in a vacuum, would produce between these conductors a force equal to 2 x 10−7 Newton per metre of length. • What’s a Newton?→ 1kg-m/(s2) Chabot College Mathematics 10 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Kelvin (Temperature) Defined Thermodynamic temperature (Kelvin) The unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. 273.16K = 0.0098 °C Room Temperature (72 °F) is about 295.5 Kelvins NO “Degree” Sign Used with the Kelvin Unit Chabot College Mathematics 11 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx mole (amt of Substance) Defined Amount of The mole is the amount of substance of a system which Substance contains as many elementary (mole) entities as there are atoms in 0.012 kilograms of carbon 12. 1 mole = 6.023x1023 entities • entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. Chabot College Mathematics 12 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Luminous Intensity Defined The luminous intensity, in a given Light direction, of a source that emits Brightness monochromatic radiation (one(candela) color light) of frequency 540 x 1012 Hertz (555 nm) and that has a radiant intensity in that direction 555nm color of 1/683 watt per steradian The are 4 (12.57) Steradians in a Sphere • 1 Str = 7.96% of the Sphere Surface Chabot College Mathematics 13 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Units Have Evolved Candela Predecessor based on a Flame • Hence the Name Temperature Based on Freezing points • Water • Platinum Second Based on the Sidereal (standard) day Chabot College Mathematics 14 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Units Have Evolved History of the Meter (or Metre) • One ten millionth of the distance from the North pole to the equator. • The distance between two fine lines engraved near the ends of a platinum-iridium bar • 1 650 763.73 wavelengths of a particular orange-red light emitted by atoms of krypton-86 (86Kr). • The length of the path traveled by light in a vacuum during a time interval of 1/299 792 458 of a second. Chabot College Mathematics 15 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx SI Derived Units The Seven Base Units May be Algebraically Combined to Produce “Derived Units” units of distance • e.g.: Units of velocity units of time meters Several Derived seconds Units have Special Usefulness and are m/s thus Given their OWN Names Chabot College Mathematics 16 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Some Derived Units Derived quantity Name Symbol Expression in terms of other SI units Expression in terms of SI base units plane angle radian (a) rad - m·m-1 = 1 (b) solid angle steradian (a) sr (c) - m2·m-2 = 1 (b) frequency hertz Hz - s-1 force newton N - m·kg·s-2 pressure, stress pascal Pa N/m2 m-1·kg·s-2 energy, work, quantity of heat joule J N·m m2·kg·s-2 power, radiant flux watt W J/s m2·kg·s-3 electric charge, quantity of electricity coulomb C - Chabot College Mathematics 17 s·A Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Some (more) Derived Units Derived quantity Name Symbol Expression in terms of other SI units Expression in terms of SI base units electric potential difference, electromotive force volt V W/A m2·kg·s-3·A-1 capacitance farad F C/V m-2·kg-1·s4·A2 electric resistance ohm V/A m2·kg·s-3·A-2 electric conductance siemens S A/V m-2·kg-1·s3·A2 magnetic flux Weber Wb V·s m2·kg·s-2·A-1 magnetic flux density tesla T Wb/m2 kg·s-2·A-1 inductance henry H Wb/A m2·kg·s-2·A-2 Celsius temperature degree Celsius °C luminous flux lumen lm cd·sr (c) illuminance lux lx lm/m2 Chabot College Mathematics 18 - K m2·m-2·cd = cd m2·m-4·cd = m2·cd Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx SI prefixes – A form of ShortHand Factor Name Symbol Factor Name Symbol 1024 yotta Y 10-1 Deci d 1021 zetta Z 10-2 Centi c 1018 exa E 10-3 milli m 1015 peta P 10-6 micro µ 1012 tera T 10-9 nano n 109 giga G 10-12 pico p 106 mega M 10-15 femto f 103 kilo k 10-18 atto a 102 hecto h 10-21 zepto z 101 deka da 10-24 yocto y Chabot College Mathematics 19 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Derived Units Family Tree No Special Names Chabot College Mathematics 20 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Old (and Tired) Unit Sets MKS • Stands for Meter-Kilogram-Second as the Most Common Units – Predecessor to The SI System CGS • Means Centimeter-Gram-Second – Still Widely Used IPS, FPM, FPH • Inch-Pound-Sec, Foot-Lb-Min, Ft-Lb-Hour Chabot College Mathematics 21 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx American Engineering System, AES – Still in (declining) Use Fundamental Dimension length foot (ft) mass pound (lbm) force pound (lbf) time second (sec) electric charge [Q] coulomb (C) absolute temperature degree Rankine (oR) luminous intensity candela (cd) amount of substance mole (mol) Chabot College Mathematics 22 Base Unit Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Conservation of Units Principle of conservation of units: • Units on the LEFT side of an equation MUST be the SAME as those on the RIGHT side of an Equation Then Have Dimensional Homogeneity • Needed to Prevent “Apples & Oranges” Confusion – e.g., I Buy 100 ft of Wire at One Store and 50 m at another; how much total Wire do I have? (It’s NOT “150”) Chabot College Mathematics 23 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Unit Conversion by Chain-Link To Determine the Amount of Wire I have I Need to Convert to Consistent (Homogeneous) Units Start by Thinking About the Definition of “1” • AnyThing divided by ITSELF = “1” • Now Consider a “minute” 60 Seconds 1 minute therefore 1 min 1 60 sec or 60 sec 1 1 min Read as “60 Seconds per minute” Chabot College Mathematics 24 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chain-Link Unit Conversion Units can also be Multiplied and Divided in a manner similar to Numbers • This how we get, say, “Square Feet” – e.g.; Consider an 8ft x 10ft Engineer’s Cubicle in Dilbert-Land. How Much WorkSpace Does the Engineer Have? WrkSpc 8ft x 10 ft 8x10 ftxft 80 ft Now Back to the Wire • Want to Know how many FEET of Wire I have in Total Chabot College Mathematics 25 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx 2 Chain-Link Unit Conversion cont. Check in Table 16.8 and Find “3.2808 ft = 1meter (“3.2808 ft per meter”) • Multiply the 50m by this special Value of 1 3.2808 feet 50 meter 1 50 meter 164.04 feet 1 meter Can “Cancel” The Units by Division So then the Total Wire = 264 ft Chabot College Mathematics 26 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chain Link Examples A World-Class Sprinter can Run 100m in 10s. • How Fast is this in MPH? 100 m 3.2808 ft 1 mile 60 s 60 min miles 22.37 10 s 1m 5280 ft 1 min 1 hr hr Gasoline In Seoul Costs 1840 Korean-Won (W) for one Liter of Regular Unleaded • How Much is this in $ per Gallon – Find Currency Exchange Rate → $1 = 1150 W 1840 W 1$ 28.317 Liter 1 ft 3 $ 6.06 3 1 liter 1150 W 1 ft 7.48 Gal Gal Chabot College Mathematics 27 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Several Forms of “1” Unit Conversion Factors 1 mile = 5280 feet 1 meter = 3.281 feet 1 foot = 12 inches 1 yard = 3 feet 1 lb = 4.448 Newtons 1 m2 = 1973.5 Circular inch 1 cup = 48 TeaSpoon $1 = 0.787 € 1 Btu = 1054.4 Joule 1 Watt = 1 Joule/sec 1 HorsePower = 2545 Btu/hr 1 km = 1000 meters 1 furlong = 220 yards °F = 1.8x°C + 32 1 Acre = 43,560 ft2 $1 = 16,030 Viet Nam Dong 1 hour = 60 min 1 min = 60 sec 1 gallon = 3.785 liters 1 ft3 = 7.4805 gallons 1 Pascal = 1 Newton/m2 1 HorsePower = 550 ft-lb/s 1 lb = 16 ounces $1 = 10.825 Mexican Pesos ANYTHING Divided by ItSelf = 1 43560 ft 2 550 ft lbs s 1054.4 J 10.825 MXNs 1 1 1 1 acre 1 HP 1 Btu 1 USD Chabot College Mathematics 28 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Units – Exponent Properties a1 = a 0 as an exponent a0 = 1 Negative Exponents (flippers) an 1 n, a a n bm a n, m b a b The Product Rule a m a n a mn . The Quotient Rule am a mn . n a The Power Rule (am)n = amn The Product to a Power Rule (ab)n = anbn The Quotient to a Power Rule Chabot College Mathematics 29 n n a a n. b b n b a n This summary assumes that no denominators are 0 and that 00 is not considered. For any integers m and n 1 as an exponent Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Raising units to POWERS Start again with 1 1 1 1 1 2 3 n Thus have 1728 “cubic inches” per “Cubic Foot” Can do the SAME What’s a “Cubic Thing with Units. Yard” in “Cubic 3 3 3 Feet”? 12 inches 12 inches 3 3 1 1 3 3 3 3 3 feet 3 feet 1 foot 1 foot 1 And 123 = 1728 so 3 3 123 inches 1728 inches 1 3 3 3 1 foot 1 foot Chabot College Mathematics 30 1 yd 13 yd 3 So have 27 cubic-ft per cubic-yd • NOT “9” Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx 7 inches, Water Column Ms. Ezersky noted that Natural Gas is delivered by PG&E to home at a pressure of 4-7 “inches of Water Column” A U-Tube Manometer can Measure Pressure Differences in Inches of Water Column This is a unit of pressure, Just Like Pascals or psig Chabot College Mathematics 31 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx 7 inches, Water Column To Calc the “in-WC” pressure we need to know some Engineering Physics From ENGR36 Pg h For Liquid Water at Room Temperature and Pressure w 9790 N m Now find 7 in-WC in psig • Where – 𝛾 ≡ Liquid SPECIFIC WEIGHT – h ≡ Liquid Column Height Chabot College Mathematics 32 3 Natural Gas @ 9.5 inWC Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx 7 inches, Water Column Convert out the N & m N N in Pg w h w 9790 3 7in 68530 3 m m N in 1lb 1m 1ft Pg 68530 3 m 4.448N 3.281ft 12in 3 3 lb in 1m3 1ft 3 lb Pg 15407 3 0.2524 2 3 3 m 35.32ft 1728in in Chabot College Mathematics 33 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx White Board Examples cont. The USA FDA recommends that Adults consume 2200 Calories per Day • What then is the “Power Rating” of a Grown Human Being? – Note that there are TWO types of “Calories” 1. The Amount of Heat Required to Raise the Temperature of 1 GRAM of water by 1 °C (or 1 Kelvin) Often Called the Gram-CAL; This is what is in the Text 2. The Amount of Heat Required to Raise the Temperature of 1 KILOgram of water by 1 °C Often Called the kgCAL or kiloCal; This is what you read on the side of Food Packaging Chabot College Mathematics 34 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Tire Pressure Many AutoMobile Tires have a Maximum Pressure Rating of About 44 psig. Convert 44 psi to kiloPascals (kPa) Chabot College Mathematics 35 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Ton of Refrigeration During his Presentation Mr. Ian McClaren of SouthLand Industries described the “Ice Storage” Cooling System Behind Bldg-1800. He Noted that the Cooling Power of this system was Rated in “Tons” What is a “Ton” of Cooling Power Chabot College Mathematics 36 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Ton of Refrigeration A TON of the refrigeration is defined, roughly, as the COOLING effect of melting 2000 lbs of water ICE over a 24 HOUR Period • From PHYS4C (or ASHRAE HandBook) find that the “Latent Heat of Fusion” for ice is 333.55 kJ/kg On WhtBoard Convert a “Ton of Refrigeration” to • kW and Btu/hr Chabot College Mathematics 37 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx White Board Examples A 2003 Chevy z06 corvette • Has a 5.7 Liter V8 Engine – What is the Engine Displacement in cubic-inches? • Develops 410 HP – What is the Power in Watts? A the Maximum recommended pressure for many 65R15 tires is 44 psi (lbs per sqinch; NOT lbs) • What is this Max Pressure in kPa? Chabot College Mathematics 38 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Percent (%) – What it is? Divide the Word into Two Parts • “PER” ≡ DIVIDE • “CENT” ≡ HUNDRED – e.g., 1¢ (1 cent) = 1/100th of a Dollar ($) Example – Home Prices • The median home price in the USA Was 13.6% Lower in 2009 than in 2008 – Meaning for every $100k of home value in 2008, the Market prices Decreased by $13.6k in 2009 Chabot College Mathematics 39 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx PerCent Notation n% Means But by Decimals n 100 1 0.01 100 • “n per hundred” So n% And n 1 n 100 100 Chabot College Mathematics 40 n 0.01n 100 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx PerCent as a UNIT 100% Means 100 1 100 In other Words 100% 1 1 Chabot College Mathematics 41 Convert 37.3% using 100%/1 = 1 1 37.3% 0.373 100% Suggest Using Every Time 1 100% 1 or 1 100% 1 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Example – Covert to Decimals Convert to Decimals a) 94% b) 7.6% Solutions 1 1 94% 94 94 0.01 0.94 100% 100 1 1 7 .6 % 7 .6 7.6 0.01 0.076 100% 100 Chabot College Mathematics 42 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Convert TO %-Notation Convert a) 2.39 b)0.2 c) 3/8 Solutions Using 100%/1 = 1 100% 2.39 2.39 100 % 239% 1 100% 0 .2 0.2 100 % 20% 1 100% 3 0.375 0.375 100 % 37.5% 0.375 1 8 Chabot College Mathematics 43 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx PerCent Change ≡ Δ% – Negative Δ% → the Any Percentage New (or Changed) Change; the “∆%”, value is Less Than than the BaseLine in any quantity is expressed Relative Example to a BASELINE • My Old Car got New Baseline 100% 37mpg. My new % truck gets 29mpg Baseline 1 • Δ% can be either Positive or Negative – Positive Δ% → the New (or Changed) value is GREATER than the BaseLine Chabot College Mathematics 44 – Find %-Change in the Fuel Efficiency 29mpg 37mpg 100% % 37mpg 1 8 100% % 21.6% 37 1 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Example % Change The Graph at right shows the magnetic B-H behavior of an Iron-Silicon Alloy The Graph To finch the %-Change in Flux Density when the Field Strength changes from 20 Amps per meter (A/m) to 90 A/m Chabot College Mathematics 45 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Example % Change 1.60 % % 1.22 New Baseline 100% Baseline 1 1.60 A/m 1.22 A/m 100% 1.22 A/m 1 % 0.38 100% 1.22 1 % 31.1% Thus B increases by 31.1% when H increases by 350% 90 Chabot College Mathematics 46 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx All Done for Today How to Spend the Calories Chabot College Mathematics 47 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 48 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 49 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Tire Pressure: 44 psi → kPa Chabot College Mathematics 50 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 51 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 52 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 53 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 54 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 55 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx Chabot College Mathematics 56 Bruce Mayer, PE BMayer@ChabotCollege.edu • MTH1516_Sp14_Using_Units.pptx