key for exercises in the text book,unit 2 (b9)

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1、KeyforExercisesintheTextBookComprehendingAnswerkeyforExercise1:1BA2Speedandtimeareimportantinfindingoutthelongitudeofashipbecausetheearthmovesfifteendegreeswestwardseveryhour.Ifyouyou’reyourdirection,speedandtime,youcanworkouttheapproximatelongitudeorchangeinyourpositioninrelationtothestars.3Th

2、epositionofthesunandstarsareusefulforworkingoutlatitudebecausetheyarefixedpointsintheskyandtheirmovementsinrelationtotheeartharealreadyknown.Sotheycanbeusedtomeasureaship'sposition.SuggestedanswerstoExercise2:1Thesailorswouldneedtobeexcellentnavigators,abletocopewithbothhotandcoldweather,experi

3、encedinsailingthroughverybadweatherandabletoco-operateinateam.2Iwouldanticipateveryhotweather(aroundtheequator),coldweather(aroundtheCapeofGoodHope),verystormyseas(aroundtheCape),andproblemswithfoodandwater(unlesshelpedbylocalnativesthewatermaybecontaminatedandthefoodscarce),etc.AnswerkeyforExe

4、rcise3:Whatwouldyoudoif:PlanofactionYouwerefarfromlandandastormarose.waittillthestormisover,andthenfindyournewpositionandreturntoyouroriginalcourseYouknewyourlatitudebutdidn'tyou’reyourlongitude.useknotstofindyourspeedandworkoutyourapproximatelongitudeYouwereblownoff-course.usethecompassandthea

5、strolabe,quadrantorsextanttofindoutyourposition,returntoyourformercourseWhatwouldyoudoif:PlanofactionYouwereoffshorebutyouneededmorefoodandwater.follownestingbirdstoshore;lookforspecialcloudformationsorfogoverstreamstofindlandYouwantedtokeepastraightcourse.useacompassYouwerelostwithnolandinsigh

6、t.measureyourpositionusingthesunorstars;lookforseabirds,cloudformations,fogorseaweedtoshowthatlandisnearbyAnswerkeyforExercise4:2freshseaweed,nestingbirdsreturninghomeintheeveningorfog3seacurrentsortidesandwinds41measuringtimeandspeed2compassandcomplicatedmathematicaltables5Bearingcircle:tocomp

7、aretheheightofthesunnowwiththepositionofthesunatmidday.Astrolabe:tocomparethepositionoftheshipinrelationtosomestarsorthesun.Quadrant:amorepreciseformoftheastrolabe,tomeasurehowhighstarsareabovethehorizon,andcomparethatmeasurementw