4E Phy Prelim 2021_ans

C O N F I D E N T I A L 2021Prelim▪ 6091Physics▪ Secondary4E Paper 1(40marks) [1] ×40 1 2 3 4 5 6 7 8 9 10 C C C A B C C B C B 11 12 13 14 15 16 17 18 19 20 C D B B C B C B A D21 22 23 24 25 26 27 28 29 30 B C A B C A C D B A31 32 33 34 35 36 37 38 39 40 B A A C C C D A B B Paper 2 SectionA(50marks) 1 (a)(i) The weight of Ypullingitdownis equal to the resultant force due tothetensionsinthestringspullingit up.SinceresultantforceonYiszero,Yremainsatrest. B1 (a)(ii) scale=1cm:0.5N resultantforceof3.5Ndrawnupwards(orweightdrawndownwards)witharrowandlabeltensionsinstringsdrawnatcorrectangleswitharrowsandlabels weightofX=2.75N[accept2.65–2.85N] M1 M1 A1 (b) The moment Y starts to drop, its gravitational potential energyconvertstokineticenergyasYacceleratesdownwards.Someofitskineticenergythenconvertstoheat andsoundenergyasYdoesworkagainst air resistance. B1 B1 2 (a) Theclockwisemoment duetotheforceof thefoot onthebrakepedalaboutpivot is equal totheclockwise moment due to the force on thepistonaboutpivot.Sincemoment=Fxdandthe perpendicular distance fromforce onpiston to pivot is greater thantheperpendicular distancefromforceof foot topivot,theforceonpistonisgreaterforthesamemoment. B1 B1 B1 MdmNur Hazwah Page 1 of 6

C O N F I D E N T I A L 2021Prelim▪ 6091Physics▪ Secondary4E (b) P=F/A pressureonpistonA =pressureonpistonB 6402.0 = 𝐹15 F=4800N(shownthatforceonpistonBisgreaterthantheforceof640NonpistonA) M1 A1 3 (a) n=1/sinc1.4=1/sincc=46° A1 *angle32.9°shouldbe33° (b)(i) (b)(ii) (b)(iii) n=sini/sinr1.4=sin50/sinrr =33° OnFig.3.1,drawrefractedrayfromAtoB. OnFig.3.1,drawnormalatBandreflectedrayfromBtoC.angleofreflection=33° OnFig.3.1,drawnormalatCandrefractedrayoutatC.angleofrefraction=50° B1 B1 B1 B1 (c) Thebeadsareusedtoreflectlightfallingontheroadsignsintomotorists’eyessothattheycanseethesignsclearly. B1 4 (a) Itisthedistancebetweentheopticalcentreofthelensanditsfocalpoint. B1 MdmNur Hazwah Page 2 of 6

C O N F I D E N T I A L 2021Prelim▪ 6091Physics▪ Secondary4E (b) focallength=1.9cm M1 A1(c) P: Power=energyconverted/timeR: Sincethelensisableto converge light rays onto the solar cell,itwill increasetheamount of energyabsorbedbythecell.O:Thiswill leadtoan increase in the amount of electrcial powergeneratedbythesolarcell. B1 B1 (d) P: The light rays will converge at a further distanceafterpassingthroughthelensoflongerfocallength.R: Since less light rays converge onto the solar cell,theamountofelectricalpowergeneratedbythesolarcellwillreduce.O:Thismakesthesolarcell lessefficient. B1 B1 5 (a) V =IR240=(P/V)xR240=(48/240)xRR=1200Ω M1A1 (b) P: V=IRR: Atthestart,the resistance of the lamp increasesatadecreasingrate.O:Hence, current inthelampdecreasesatadecreasingrate.R: Theresistanceof thelampthenbecomesconstant.O:Hence, current inthelampremainsconstant. B1B1B1 (c) 1Thefilamentinthesecondlampislongerthanthefirst.2Thefilamentinthesecondlampisthinnerthanthefirst. B1B1 6 (a)(i) V=IR4.20=Ix12I=0.35A A1 (a)(ii) V=6.0–4.20=1.8V V=IR1.8=0.35xRR=5.14Ω M1 A1 (b)(i) P: