Final. Mark Scheme. Physics A PHYA5/2C. (Specification 2450) Unit 5/2C: Applied Physics. General Certificate of Education (A-level) June 2011 PMT

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1 Version 1.1 Generl Certificte of Eduction (A-level) June 011 Physics A PHYA5/C (Specifiction 450) Unit 5/C: Applied Physics 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 01 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 ) nd registered chrity (registered chrity number ). Registered ddress: AQA, Devs Street, Mnchester M15 6EX.

3 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C 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 3-4 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. 3 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 3 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. 3

4 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 GCE Physics, Specifiction A, PHYA5/1, Nucler nd Therml Physics Question 1 b 33 91P nti (electron) neutrino Q P c i x = 4 1 c ii mss defect = [( ) ( )] u = u 3 energy relesed (= ) = 169 (MeV) Totl 8 Question b 7 + α 30 P + n 1 Al (1) (0) kinetic energy lost by the α prticle pproching the nucleus is equl to the potentil energy gin = r = (m) 1 4π r 3 Totl 4 4

5 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 Question 3 4 pek 8.7 (ccept ) in MeV (or pek ccept in J ) t nucleon number ccept shrp rise from origin nd moderte fll not below /3 of pek height b energy is relesed/mde vilble when binding energy per nucleon is incresed in fission (lrge) nucleus splits nd in fusion (smll) nuclei join the most stble nuclei re t pek mx 3 fusion occurs to the left of pek nd fission to the right Totl 7 Question 4 (use of ΔQ = m c ΔT) = c 14 c = 100 (J kg 1 K 1 ) b (use of ΔQ = m l + m c ΔT) = ΔT (ΔT = 38 C) 3 T = 38 C c the temperture would be higher s the ice/wter spends more time below 5 C or het trvels in the direction from hot to cold or ice/wter first gins het then loses het ny one line Totl 7 5

6 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 Question 5 grph psses through given point m 3 t 0 C stright line with positive grdient (stright) line to im or pss through 73 C t zero volume b (use of n = P V/R T) / n = (moles) c (use of men kinetic energy = 3/ K T) = 3/ (J) 3 sfs d totl internl energy = = 390 (J) 1 e 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 sequence of ides linking the motion of molecules to the pressure they exert on continer. At lest three of the first four points listed below must be given in logicl order. The description should lso show wreness of how blnce is mintined between the increse in speed nd shortening of the time intervl between collisions with the wll to mintin constnt pressure. To be in this bnd, reference must be mde to force being the rte of chnge of momentum or how, in detil, the volume compenstes for the increse in temperture. mx 6 Intermedite Level (Modest to dequte): 3 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. The cndidte provides comprehensive list of ides linking the motion of molecules to the pressure they exert on continer. At lest three of the first four points listed below re given. The cndidte lso knows thn the men squre speed of molecules is proportionl to temperture. Using this knowledge, n ttempt is mde to explin how the pressure is constnt. 6

7 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 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 ttempts the question nd refers to t lest two of the points listed below. Incorrect, inpproprite of no response: 0 mrks No nswer or nswer refers to unrelted, incorrect or inpproprite physics. Sttements expected in competent nswer should include some of the following mrking points. molecules re in rpid rndom motion/mny molecules re involved molecules chnge their momentum or ccelerte on collision with the wlls reference to Newton s nd lw either F = m or F = rte of chnge of momentum reference to Newton s 3 rd lw between molecule nd wll relte pressure to force P = F/A men squre speed of molecules is proportionl to temperture s temperture increses so does chnge of momentum or chnge in velocity compensted for by longer time between collisions s the temperture increses s the volume increses the surfce re increses which reduces the pressure Totl 14 7

8 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 GCE Physics, Specifiction A, PHYA5/C, Applied Physics Question 1 the (totl) ngulr momentum (of system) remins constnt provided no externl torque cts (on the system) 1 b i (s core rdius decreses M of I of core decreses) I ω must remin constnt I decreses so ω increses nd greter ω mens shorter period of rottion or less time for one revolution b ii 0.4 mr 1 π/t 1 = 0.4 mr π/t T /T 1 = R /R 1 T = (1 103 ) ( ) = 0.33 s sf or 0.4 m ( ) ω 1 = 0.4 m ( ) ω 4 ω 1 = π/t = π/( ) = rd s 1 ( ) leding to ω = 0 rd s 1 [19.3 if used] T = π/ω = 0.31 s ( sf throughout) sf [0.33 s if rd s 1 nd 19.3 rd s 1 used] Totl 7 8

9 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 Question 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 logicl explntion which recognises tht energy stored depends on moment of inerti nd ω nd tht moment of inerti itself depends on the mss nd how the mss is distributed bout the xis of rottion, quoting nd explining Σmr. They will pprecite tht high mss will result from using high density mteril nd they will relise tht incresing the rdius lone will not necessrily increse M of I for given mss, but the shpe (eg spoked or not) might. They will refer to mens of promoting high speed nd my pprecite why there is limit to the mximum speed depending on tensile strength. Intermedite Level (Modest to dequte): 3 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 comprehensive nd logicl explntion which links moment of inerti nd ω to energy stored nd will discuss the fctors tht ffect the moment of inerti, but there my be errors in their understnding. They will probbly refer to the need to reduce friction but they my not stte how this my be done. There my be some reference to the density or strength of the mterils used, but the links with energy storge or M of I will be vgue. The nswer should be dequtely or wellpresented in terms of spelling, punctution nd grmmr. 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 recognises tht energy storge depends on speed nd M of I, but my not link M of I dequtely to rdius or mss or the distribution of the mss. They my confuse power or ngulr momentum with energy. The nswer my lck coherence nd my contin significnt number of errors in terms of spelling nd punctution. Incorrect, inpproprite of no response: 0 mrks No nswer or nswer refers to unrelted, incorrect or inpproprite physics. 9

10 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 Sttements expected in competent nswer should include some of the following mrking points. Linking E to ω Linking E to Σmr Importnce of shpe; put more m t greter r, use thin xle High density mteril promotes high m for given size Friction reduced by low-friction (eg mgnetic- or ir-) berings nd smooth outer surfce Rottionl speed limited by tensile strength of mteril Reference to centripetl force Frictionl torque increses with rottionl speed Some nswers might refer to dverse gyroscopic effects or need for perfect blnce b i ΔE = ½ I (ω 1 ω ) = ( ) = J 1 b ii P = E/t = = W 6.6 ccept 85 kw if unit is chnged in nswer line from W to kw 1 b iii b iv Tθ = ΔE T = P/ω ve 4750 N m or T = I α = ( ) = 18 N m 6.6 θ = /18 = rd = 4900 rev π or θ = ½ ( ) 6.6 = rd = 4900 rev or θ = ω 1 t ½ α t = ½ = rd = 4900 rev Totl 1 10

11 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 Question 3 i use of PV/T = constnt P D V D T A P A V A = = 500 K ii Q = ΔU + W ΔU = 0 Q = W = 173 J b i work out = = 69 J 1 b ii efficiency = 69/173 = 0.40 or 40% η mx = (T H T C )/T H = ( )/500 = 0.39 or 40% c V /10-3 m A D 0.5 B C T / K rectngle in correct position letters correct plce (rrows optionl) d isotherml process impossible unless very slow or vi perfect conductor engine would hve to stop for constnt volume processes to tke plce regenertor would lose het to surroundings (unless perfectly insulted) long time needed for het to trnsfer from regenertor to working fluid regenertor would need to be very lrge/lrge surfce re for het trnsfer to tke plce quickly ccept other sensible suggestions do not ccept het loss to surroundings or friction ny two Totl 11 11

12 Mrk Scheme Generl Certificte of Eduction (A-level) Physics A PHYA5/C June 011 Question 4 i = 500 W 1 ii 500 Q out = 780 or 3. = Q out = 170 W Q in = 500 Q in Q out 500 Q out 1 giving Q out = 170 W b het pump does deliver more energy thn is input s work on the system but there must lso be energy input from cold spce obeys conservtion of energy becuse work done plus energy from cold spce (or equivlent, eg ground) equls energy by het trnsfer to hot spce (or equivlent) obeys second lw becuse (reversed het engine) opertes between hot nd cold spces [ccept source nd sink ] mx 3 work done on the system requires energy trnsfer (from het engine elsewhere) so overll result is spreding out of energy [owtte] Totl 5 UMS conversion clcultor 1

Final. Mark Scheme. Physics A PHYA5/2A. (Specification 2450) Unit 5/2A: Astrophysics. General Certificate of Education (A-level) June 2011 PMT

Final. Mark Scheme. Physics A PHYA5/2A. (Specification 2450) Unit 5/2A: Astrophysics. General Certificate of Education (A-level) June 2011 PMT Version 1.1 Generl Certificte of Eduction (A-level) June 011 Physics A PHYA5/A (Specifiction 450) Unit 5/A: Astrophysics Finl Mrk Scheme Mrk schemes re prepred by the Principl Exminer nd considered, together