01-Chap-1-Introduction-to-Eng-Calculations.pptx

Introduction to Engineering Calculations

Introduction to Engineering CalculationsChapter 1Unit and Conversion1What are in this chapter?2Topic outcomesAt the end of Chapter 1, you should:

Identify the units commonly used to express in SI and British units.Convert one set of units in a function or equation into another equivalent set for mass, length, area, volume, time, energy and force using conversion factor tables.

3Systems of Units4Systems of UnitsBase units - units for the dimensions of mass, length, time, temperature, electrical current, and light intensity.Multiple units- multiple or fractions of base unit. E.g.: for time can be hours, millisecond, year, etc.Derived units - units that are obtained in one or two ways;By multiplying and dividing base units; also referred to as compound units. Eg.: ft/min (velocity), cm2(area), kg.m/s2 (force) As defined equivalent of compound unit. (Newton = 1 kg.m/s2)5Base Units6Multiple SI UnitsPrefixFactortera (T) 10 12giga (G) 10 9mega (M)10 6kilo (k)10 3centi (c)10 -2milli (m)10 -3micro ()10 -6nano (n)10 -97Derived SI UnitsQuantityUnitSymbolEquivalent to the Base UnitVolumeLiterL0.001 m3 = 1000 cm3ForceNewton (SI)Dyne (CGS)N1 kg m s-21 g cm s-2PressurePascalPa1 N m-2Energy/ WorkJouleCalorieJcal1 N m = 1 kg m2 s-24.184 J = 4.184 kg m2 s-2PowerWattW1 J s-1 = 1 kg.m2 s-38Units and DimensionsDimensions are:Properties that can be measured such as length, time, mass, temperature. Properties that can calculated by multiplying or dividing other dimensions, such as velocity (length/time), volume, density. Units are used for expressing the dimensions such as feet (ft) or meter (m) for length, hours/seconds (hr/s) for time.Contain significant amount of information

936 mg1 g=0.036 g1000 mg0.001 is a conversion factorConversion of UnitsA measured quantity can be expressed in terms of any units having the appropriate dimension.To convert a quantity expressed in terms of one unit to equivalent in terms of another unit, multiply the given quantity by the conversion factor.Conversion factor a ratio of equivalent values of a quantity expressed in different units.Let say to convert 36 mg to gram

10Dimensional EquationTo convert a quantity with a unit to its equivalent in term of other units, set up a dimensional equation:Write the given quantity and units on leftWrite the units of conversion factors that cancel the old unit and replace them with the desired unitFill the value of the conversion factorsCarry out the arithmetic value

11Convert 1 cm/s2 to km/yr2Dimensional Equation12Dimensional EquationConvert 8 mm2 to in2?

13Convert 4 kg/m3 to lbm/ft3Dimensional Equation14Dimensional EquationNanotechnology is the generic term that refer to the synthesis and application of such small particles. An example of a semiconductor is ZnS with a particle diameter of 1.8nm. Meanwhile, our 5 cent coin has a diameter of 16mm. How many times 5 cent coin is bigger than this nano particle?

15Exerciseu = fluid velocityp = pressure drop = densityc = constant

What is the unit for constant c?

16Force and WeightForce is proportional to product of mass and acceleration (i.e. F = m x a) Usually defined using derived units ;1 Newton (N)= 1 kg m s-21 dyne= 1 g cm s-21 Ibf= 32.174 Ibm ft s-2Weight of an object is force exerted on the object by gravitational attraction of the earth i.e. force of gravity, g.gc is used to denote the conversion factor from a natural force unit to a derived force unit.

17Force and Weight - ExampleGiven the density of 2 ft3 water is 62.4 lbm/ft3. At the sea level, the gravitational acceleration is 32.174 ft/s2. What is the weight of the water in lbf?

18What have you learned?19