GE 121 – Engineering Design Engineering Design GE121 UNITS Lecture 9A

GE 121 – Engineering Design Units  All units should be standard Systeme Internationale (SI or metric)  gram, meter, liter, second, volt, watt, pascal, newton, etc.  Or the approved abbreviation: g, m, l (or L), s, V, W, Pa, N, etc. Units named after a person are capitalized when abbreviated but not in full E.g. abbreviation for ampere is A not amp  Choose magnitude of units that make sense  E.g.: km/hr for vehicle speeds rather than m/s in a report dealing with transportation.  SI standard increments are in multiples of 10 3 Femto, pico, nano, micro, milli, kilo, mega, giga, tera Abbreviations are lower case for 1 (except kilo): f, p, n, μ, m, k or K, M, G, T E.g. 51 mm NOT 5.1 cm  Make sure your units are consistent or there may be devastating results

GE 121 – Engineering Design Base Units  Length (L)  SI: km, m (meter), mm, etc.  Time (T)  SI: s (second) Use fractional seconds (ms or microseconds) but not ks or Ms  minute, hour, day, week, etc.  Mass (M)  SI: g (gram), kg, ng

GE 121 – Engineering Design Derived Units  Area (L 2 )  SI: hectare, m 2, etc.  Acres: this is an exception since it is in widespread use in western Canada  Volume (L 3 )  SI: m 3, L or l, mL, etc.

GE 121 – Engineering Design Derived Units  Speed (L/T)  SI: m/s, km/hr, etc.  Acceleration (L/T 2 or LT -2 )  SI: m/s 2 or ms -2

GE 121 – Engineering Design Conversions a systematic approach is best to eliminate errors e.g. Convert 6.7 in to millimeters. 6.7 in = 25.4 mm 1 in 6.7 in = (6.7)(25.4) mm = mm = 1.7 × 10 2 mm

GE 121 – Engineering Design furlong fortnight × 1 fortnight 14 days Conversions Given the conversions 1 furlong = 220 yards, 1 m = yards, 1 fortnight = 14 days, calculate the speed in m/s of an animal which moves at 5 furlongs/fortnight. 5 furlongs/fortnight = 220 yards furlong 1 m yards = (5)(220)/((1.097)(14)(24)(3600)) m/s = × m/s = 8 × m/s or 800 μm/s 1 day 24 hours 1 hour 3600 s

GE 121 – Engineering Design Conversions Your car has a highway mileage of 35 mpg (miles/US gallon ). What is its mileage in L/100 km? (1 mile = km) (1 US gallon = L) Ans: 6.7 L/100 km