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21HW

21HWDue:11:59pmonWednesday,December10,2014Youwillreceivenocreditforitemsyoucompleteaftertheassignmentisdue.GradingPolicy

Exercise21.2Lightningoccurswhenthereisaflowofelectriccharge(principallyelectrons)betweenthegroundandathundercloud.Themaximumrateofchargeflowinalightningboltisabout20, 000 C/sthislastsfor100 s orless.

PartAHowmuchchargeflowsbetweenthegroundandthecloudinthistime?Expressyouranswerusingthreesignificantfigures.ANSWER:Q

= 2.00 C

Correct

PartBHowmanyelectronsflowduringthistime?Expressyouranswerusingthreesignificantfigures.ANSWER:ne

= 1.251019

Correct

Exercise21.19Threepointchargesarearrangedalongthexaxis.Chargeq 1 =+3.00Cisattheorigin,andchargeq 2 =5.00Cisatx=0.200m.Chargeq 3 =8.00C.

PartAWhereisq 3 locatedifthenetforceonq 1 is7.00Ninthex direction?ANSWER:x3

= 0.144 m

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Exercise21.50Apointchargeq 1 =4.00nCisatthepointx=0.60m,y=0.80m,andasecondpointchargeq 2 =+6.00nCisatthepointx=0.60m,y=0.

PartACalculatethemagnitudeofthenetelectricfieldattheoriginduetothesetwopointcharges.ANSWER:E

= 132 N/C

Correct

PartBCalculatethedirectionofthenetelectricfieldattheoriginduetothesetwopointcharges.ANSWER:

= 167 counterclockwisefrom+ xaxis

Correct

Problem21.02

PartAA1.0Cpointchargeis15 mfromasecondpointcharge,andtheelectricforceononeofthemduetotheotheris1.0

N.Whatisthemagnitudeofthesecondcharge?(k

= 1/4 0 = 8.99 10

9

Nm2/C2)

ANSWER:

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1.0

C

10

nC

25

C

25

nC

0.025

C

Correct

Exercise21.22Twopointchargesareplacedonthexaxisasfollows:chargeq 1 =3.99nCislocatedatx=4.98nCisatx = 0.295m.

=

0.196m,andchargeq 2

PartAWhatisthemagnitudeofthetotalforceexertedbythesetwochargesonanegativepointchargeq 3 =5.99nCthatisplacedattheorigin?ANSWER:F

= 2.51106 N

Correct

PartBWhatisthedirectionofthetotalforceexertedbythesetwochargesonanegativepointchargeq 3 =5.99nCthatisplacedattheorigin?ANSWER:tothe+ xdirectiontothexdirectionperpendiculartothexaxistheforceiszero

Correct

Exercise21.17http://session.masteringphysics.com/myct/assignmentPrintView?assignmentID=3302247

nC

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Threepointchargesarelocatedonthepositivexaxisofacoordinatesystem.Chargeq 1 =1.5nCis2.0cmfromtheorigin,chargeq 2 =4.0nCis4.0cmfromtheoriginandchargeq 3 =6.0nClocatedattheorigin.Whatisthenetforce((a)magnitudeand(b)direction)onchargeq 1 =1.5nCexertedbytheothertwocharges?

PartAExpressyouranswerusingtwosignificantfigures.ANSWER:F

= 3.4104 N

Correct

PartBANSWER:

= 0 counterclockwisefromthe+x direction

Correct

Exercise21.1Excesselectronsareplacedonasmallleadspherewithamassof7.55gsothatitsnetchargeis3.10109C .

PartAFindthenumberofexcesselectronsonthesphere.ANSWER:ne

= 1.941010

Correct

PartBHowmanyexcesselectronsarethereperleadatom?Theatomicnumberofleadis82 ,anditsmolarmassis207 g/mol .ANSWER:

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n lead

= 8.821013

Correct

Exercise21.25Aprotonisplacedinauniformelectricfieldof3000N/C.

PartACalculatethemagnitudeoftheelectricforcefeltbytheproton.ANSWER:F

= 4.801016 N

Correct

PartBCalculatetheproton'sacceleration.ANSWER:a

= 2.871011 m/s 2

Correct

PartCCalculatetheproton'sspeedafter1.20s inthefield,assumingitstartsfromrest.ANSWER:v

= 3.45105 m/s

Correct

Exercise21.26Aparticlehasachargeof2.85nC.http://session.masteringphysics.com/myct/assignmentPrintView?assignmentID=3302247

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PartAFindthemagnitudeoftheelectricfieldduetothisparticleatapointlocatedadistance0.270mdirectlyaboveit.ANSWER:E

= 351 N/C

Correct

PartBFindthedirectionoftheelectricfieldduetothisparticleatapointlocatedadistance0.270mdirectlyaboveit.ANSWER:upawayfromtheparticledowntowardtheparticle

Correct

PartCAtwhatdistancefromthisparticledoesitselectricfieldhaveamagnitudeof12.8N/C?ANSWER:L

= 1.41 m

Correct

Exercise21.47Threenegativepointchargesliealongalineasshowninthefigure.

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PartAFindthemagnitudeoftheelectricfieldthiscombinationofchargesproducesatpointP ,whichlies6.00the2.00 Cchargemeasuredperpendiculartothelineconnectingthethreecharges.

cm

from

ANSWER:E

= 1.04107 N/C

Correct

PartBFindthedirectionoftheelectricfieldthiscombinationofchargesproducesatpointP ,whichlies6.00the2.00 Cchargemeasuredperpendiculartothelineconnectingthethreecharges.

cm

from

ANSWER:outward2.00toward2.00

C

C

CorrectScoreSummary:Yourscoreonthisassignmentis98.8%.Youreceived34.58outofapossibletotalof35points.

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