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# notesu1u2 - "The Language of Engineering" Engineers work in...

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"The Language of Engineering" Engineers work in the real world. They need a language to describe that world - to quantify it and to model it. The language of Engineering is largely based on Mathematics (8.01, 02, 03) but there are a few other important concepts that are common to several should include a fair amount of material from 8.01 Dimensions and Units branches of engineering. We are going to teach you these as "Unified Lectures". This A dimension is a physical quantity which can be measured directly. A collection of dimensions are used as the basis for a system of units System (now a misnomer) See inside cover of Crandall, Dahl, & Lardner Length [L] Time [T] Mass [M] Current [C] Temperature [ e ] Luminous Intensity (I) Amount (n) UNITS m Also(nm, mm, mn, km…) s (not Sec's - except in S&S!) Kg (g) A Ampere K (not o centigrade) Cd (Candela) M Mole DIMENSIONS (Fundamental in SI) Units quantify dimensions We will use two systems of units: SI (metric) and British Dimensions of other quantities are derived: Example: Newton's Law ± L ² FM a = ³ M T 2 µ ´ Force is a derived unit in SI

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In British System force is a fundamental unit: Dimension SI (Unit) English Unit Conversion Length m ft. (in) 0.305/ft Time s Sec - Mass Kg Slug 14.6 Kg/slug Force N Lb. 4.45N/lb. Pressure Pa (Pascal) psi 6900 Pa/Psi 2 1 pound = 1 Slug ft/S 2 1 Pascal = 1 N/m 2 2 Same Dimensions, Different Units Be VERY careful to give Units. (You many know this but the Mars Climate Orbiter Team did not!) Be very careful to use consistent magnitudes. km A m × 10 3 Use dimensions as a check. ? = energy mass speed of light 2 ML T < 2 = M [ LT < 1 ] ? Clearly ? = 2 Which can allow us to identify the controlling physical quantities in unfamiliar or complicated quantities Fluid Dynamics and Thermodynamics make extensive use of dimensional analysis. Coordinate Systems Dimensions and units allow us to quantify magnitudes (Scalar quantities).
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## This note was uploaded on 01/28/2012 for the course AERO 16.01 taught by Professor Markdrela during the Fall '05 term at MIT.

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notesu1u2 - "The Language of Engineering" Engineers work in...

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