Final. Mark Scheme. Physics A PHYA2. (Specification 2450) Unit 2: Mechanics, materials and waves. General Certificate of Education (A-level) June 2011

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1 Version 1.0 Generl Certificte of Eduction (A-level) June 011 Physics A PHYA (Specifiction 450) Unit : Mechnics, mterils nd wves Finl Mrk Scheme

2 Mrk schemes re prepred by the Principl Exminer nd considered, together with the relevnt questions, by pnel of subject techers. This mrk scheme includes ny mendments mde t the stndrdistion events which ll exminers prticipte in nd is the scheme which ws used by them in this exmintion. The stndrdistion process ensures tht the mrk scheme covers the cndidtes responses to questions nd tht every exminer understnds nd pplies it in the sme correct wy. As preprtion for stndrdistion ech exminer nlyses number of cndidtes scripts: lterntive nswers not lredy covered by the mrk scheme re discussed nd legislted for. If, fter the stndrdistion process, exminers encounter unusul nswers which hve not been rised they re required to refer these to the Principl Exminer. It must be stressed tht mrk scheme is working document, in mny cses further developed nd expnded on the bsis of cndidtes rections to prticulr pper. Assumptions bout future mrk schemes on the bsis of one yer s document should be voided; whilst the guiding principles of ssessment remin constnt, detils will chnge, depending on the content of prticulr exmintion pper. Further copies of this Mrk Scheme re vilble from: q.org.uk Copyright 011 AQA nd its licensors. All rights reserved. Copyright AQA retins the copyright on ll its publictions. However, registered centres for AQA re permitted to copy mteril from this booklet for their own internl use, with the following importnt exception: AQA cnnot give permission to centres to photocopy ny mteril tht is cknowledged to third prty even for internl use within the centre. Set nd published by the Assessment nd Qulifictions Allince. The Assessment nd Qulifictions Allince (AQA) is compny limited by gurntee registered in Englnd nd Wles (compny number 6447) nd registered chrity (registered chrity number 1074). Registered ddress: AQA, Devs Street, Mnchester M15 6EX.

3 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 Instructions to Exminers 1 Give due credit for lterntive tretments which re correct. Give mrks for wht is correct in ccordnce with the mrk scheme; do not deduct mrks becuse the ttempt flls short of some idel nswer. Where mrks re to be deducted for prticulr errors, specific instructions re given in the mrking scheme. Do not deduct mrks for poor written communiction. Refer the scripts to the Awrds meeting if poor presenttion forbids proper ssessment. In ech pper, cndidtes re ssessed on their qulity of written communiction (QWC) in designted questions (or prt-questions) tht require explntions or descriptions. The criteri for the wrd of mrks on ech such question re set out in the mrk scheme in three bnds in the following formt. The descriptor for ech bnd sets out the expected level of the qulity of written communiction of physics for ech bnd. Such qulity covers the scope (eg relevnce, correctness), sequence nd presenttion of the nswer. Amplifiction of the level of physics expected in good nswer is set out in the lst row of the tble. To rrive t the mrk for cndidte, their work should first be ssessed holisticlly (ie in terms of scope, sequence nd presenttion) to determine which bnd is pproprite then in terms of the degree to which the cndidte s work meets the expected level for the bnd. QWC descriptor mrk rnge Good - Excellent see specific mrk scheme 5-6 Modest - Adequte see specific mrk scheme -4 Poor - Limited see specific mrk scheme 1- The description nd/or explntion expected in good nswer should include coherent ccount of the following points: see specific mrk scheme Answers given s bullet points should be considered in the bove terms. Such nswers without n overview prgrph in the nswer would be unlikely to score in the top bnd. An rithmeticl error in n nswer will cuse the cndidte to lose one mrk nd should be nnotted AE if possible. The cndidte s incorrect vlue should be crried through ll subsequent clcultions for the question nd, if there re no subsequent errors, the cndidte cn score ll remining mrks. 4 The use of significnt figures is tested once on ech pper in designted question or prtquestion. The numericl nswer on the designted question should be given to the sme number of significnt figures s there re in the dt given in the question or to one more thn this number. All other numericl nswers should not be considered in terms of significnt figures. 5 Numericl nswers presented in non-stndrd form re undesirble but should not be penlised. Arithmeticl errors by cndidtes resulting from use of non-stndrd form in cndidte s working should be penlised s in point bove. Incorrect numericl prefixes nd the use of given dimeter in geometricl formul s the rdius should be treted s rithmeticl errors. 6 Knowledge of units is tested on designted questions or prts of questions in ech pper. On ech such question or prt-question, unless otherwise stted in the mrk scheme, the mrk scheme will show mrk to be wrded for the numericl vlue of the nswer nd further mrk for the correct unit. No penlties re imposed for incorrect or omitted units t intermedite stges in clcultion or t the finl stge of non-designted unit question. 7 All other procedures including recording of mrks nd deling with missing prts of nswers will be clrified in the stndrdising procedures.

4 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 GCE Physics, Specifiction A, PHYA, Mechnics, Mterils nd Wves Question 1 i grdient (llow slope / steepness of the line )! 1 ii velocity 0 time single stright line sloping down from X to t! psses through zero t t 1! increses to mximum negtive vlue t t (ignore ll lines beyond t ) or llow line from zero t t 1 to positive velocity t t greter thn the initil velocity! b i bll exerts force on ground nd ground exerts force (on bll)/rection! nd these forces re equl nd opposite! (b) ii recognise tht the downwrd force is the weight of the bll (ccept grvity)! recognition tht the upwrd/rection force (on the bll) is greter thn the downwrd force on the bll! Totl 8 Question correct substitution in (v = u + s) or correct rerrngement g =!" %.&'" or #$ # ('.)'! = 9.6 (9.61 m s 1 )! b c g = W/m or W = mg (= m) nd weight is proportionl to mss/doubling the mss doubles the weight/ msses cncel /the fctor of two cncels (so g remins the sme)! bll s ccelertion will decrese/be less thn crds or crds ccelertion will be unffected/nerly constnt! ir resistnce ffects crds less or crd is more stremlined or crd does less work ginst ir resistnce! lterntive timing/(velocity/speed/ccelertion) uncertin/(inccurte /imprecise/less relible)! indiction tht full width of bll my not pss through gte/difficulty in determining length of bll pssing through gte! 1 Totl 5 4

5 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 Question i *+,!-. / 0, )1 %.)! = 17 (m s )! ii (F = m) = ecf ()(i)! = 96000! llow or for use of 17 iii N! *, & , & 58.5! = 100 (101.50, 10, ccept 101 m)! # # or use of v = u + s (= 101 m for use of 17) or s = ut + & # t (= 101.7, use of 17 gives 104) (ecf from ()(i)) iv (W = Fs) ()(ii) ()(iii) or use of & # mv! (= 1.6 to 14.7 ) b *9, :$ ;<&'< (&'&.) 0,! =.8 M (W) ecf ()(ii), ()(iii) / %.) or use of P = :! # & their nswer 5! = 14,000,000 = 14 M (W) # (m) v = (m) g (Δ) h or (loss of) KE = (gin in) PE! llow their work done from (iv) used s KE h = & #! " = 170! = or h = & # ( )1" ;.1&! ccept use of kinemtics eqution Totl 1 Question 4 i (one) force distnce between the forces! (one) force perpendiculr distnce between the lines of ction or (one) force perpendiculr distnce between the (two) forces! ii ( =) 5900! (591) (or lterntive correct method) Nm! b P = Fv = ( ) ! ( ) = 1500! (1474 W) ny number to sf! 5

6 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 c to enble comprison between stem nd horses or mill owners/engineers etc needed to know which stem engine would be suitble or would esily be ble to compre the cost/time sved or good mrketing ploy for stem engines 1 or esily understood (by industrilists or the public) or other suitble vlid reson! Totl 8 Question 5 decrese! constnt! decrese! b A stright ry (ignore rrow) reflecting to the right! reflected ngle = incident ngle! (ccept correct ngle lbels if reflected ngle is outside tolernce) c i (n = > ) use of ( 10 8 )! = %'' ( &'@ 7 = 1.47! (1.4706) (must see sf or >? #.'A ( 7 more) c ii &.A) sin θ c = &.AB'<7 or correct substitution in un-rerrnged formul! θ c = 80.4! (80.401) (80. to 80.54) ( 80 ) must see sf or more d ngle of refrction = = 9.6! sinθ = 147(06) sin 9.6! = 0.5 ecf from first mrk θ = 14 (= )! ecf from first mrk e rnge 1 to 15 due to use of rounded vlues (reduced mplitude) due to bsorption/energy loss (within the fibre)/ ttenution/scttering (by the medium)/loss from fibre! (pulse brodening cused by) multi-pth (modl) dispersion/different rys/ modes propgting t different ngles/non xil rys tke longer time to trvel sme distnce long fibre s xil rys! Totl 14 6

7 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 Question 6 suitble scle on both xes (eg not going up in s) nd > ½ spce used! 8 points correct (within hlf smll squre)! line is stright up to t lest stress = nd curve is smooth beyond stright section! b understnding tht E = grdient (= Δy/Δx)! llow y/ /x if line psses through origin = (P) (llow 0.90 to 1.1) ecf from their line in () if nswer outside this rnge nd usess y vlue.0! when vlues used from tble; two mrks cn be scored only if cndidtes line psses through them one mrk only cn be scored if these points re not on their line 7

8 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 c correct rerrngement of symbols or numbers ignoring incorrect powers of ten, eg A = :C D C! correct substitution in ny correct form of the eqution, &''''7(%.' eg =! llow incorrect powers of ten for this mrk &.;' ( &' FF 7(&.' ( &' GH 7 = ! (1.5789) (m ) Totl 8 Question 7 The cndidte s writing should be legible nd the spelling, punctution nd grmmr should be sufficiently ccurte for the mening to be cler. The cndidte s nswer will be ssessed holisticlly. The nswer will be ssigned to one of three levels ccording to the following criteri. High Level (Good to excellent): 5 or 6 mrks The informtion conveyed by the nswer is clerly orgnised, logicl nd coherent, using pproprite specilist vocbulry correctly. The form nd style of writing is pproprite to nswer the question. The cndidte provides comprehensive nd coherent description which includes; fringe spcing/seprtion w nd distnce D mesured with one instrument nmed, uses λ = I$ to obtin vlue for λ, mesures distnce J between severl mxim nd includes vlid point bout sfety. Intermedite Level (Modest to dequte): or 4 mrks The informtion conveyed by the nswer my be less well orgnised nd not fully coherent. There is less use of specilist vocbulry, or specilist vocbulry my be used incorrectly. The form nd style of writing is less pproprite. mx 6 The cndidte provides n dequte explntion tht lcks some of the essentil points. The cndidte is expected to include; w or fringes mesured or uses λ = I$ to obtin vlue for λ. They include one ccurcy J point or vlid point bout sfety. Low Level (Poor to limited): 1 or mrks The informtion conveyed by the nswer is poorly orgnised nd my not be relevnt or coherent. There is little correct use of specilist vocbulry. The form nd style of writing my be only prtly pproprite. The cndidte provides limited explntion with no more thn one or two vlid points. Incorrect, inpproprite of no response: 0 mrks No nswer or nswer refers to unrelted, incorrect or inpproprite physics. 8

9 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 The explntion expected in competent nswer should include coherent selection of the following points. Mesurements suitble mesuring instrument for w suitble mesuring instrument for D Finding the wvelength uses λ = I$ J to obtin vlue for λ explins grphicl pproch Accurcy Sfety severl fringe spces mesured centres of fringes used five or more fringes/four fringe spces mesured lrge vlue of D D greter thn or equl to m drk room repet mesurements vernier clliper for w (not clliper, not micrometer) grphicl method vrying D nd mesuring w other vlid ccurcy point void shining lser t (or ner) person lser sfety goggles void reflections wrning sign or light b (light from both sources hs) constnt phse reltionship/difference!! in phse or sme wvelength or sme frequency is one mrk c single slit then double slits to the right! single slit nd double slits lbelled! 9

10 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA June 011 d if cndidte refers to white light Young s fringes with white light; contin (different) colours or centrl white fringe or if cndidte refers to the lser; monochromtic/one colour less intense mxim wider/minim nrrower or mx or min closer together for white light compred to red lser fringes/lines/bnds etc compred to dots more intense mxim nrrower/minim wider or mx or min further prt for red lser dots for lser compred to bnds etc from ech row, one only mx! e cncelltion/wves cncel/destructive interference/destructive superposition! (light from one slit meets light from the other) in ntiphse (180 out of phse) or pth difference of ((n+) ½)λ! Totl 14 UMS conversion clcultor 10