NCEA Level 3 Physics (91524) 2015 pae 1 of 9 Assessment Schedule 2015 Physics: Demonstate undestandin of mechanical systems (91524) Assessment Citeia Achievement Achievement with Meit Achievement with Excellence Demonstate undestandin equies witin statements that typically show an awaeness of how simple facets of phenomena, concepts o pinciples elate to a descibed situation. Fo mathematical solutions, elevant concepts will be tanspaent, methods will be staihtfowad. Demonstate in-depth undestandin equies witin statements that typically ive easons why phenomena, concepts o pinciples elate to iven situations. Fo mathematical solutions, the infomation may not be diectly useable o immediately obvious. Demonstate compehensive undestandin equies witin statements that typically ive easons why phenomena, concepts o pinciples elate to iven situations. Statements will demonstate undestandin of connections between concepts. Evidence Q Evidence Achievement Achievement with Meit Achievement with Excellence ONE (a) he foce is weiht / the foce of avity / avitational foce actin towads the cente of the Eath Gavitational / weiht / avity foce actin towads the (cente of the) Eath. (Accept adial o towads the eath) (b) F GMm 6.67 10 11 5.97 10 24 300 2 (4.22 10 7 ) 2 67.1 N F 67.1 N
NCEA Level 3 Physics (91524) 2015 pae 2 of 9 (c) Gavitational foce must be equal to the centipetal foce equied at that adius so F F c he avitational foce povides a centipetal foce so F c F Use of v GM to pove mv 2 GMm 2, so v GM v 6.67 10 11 5.97 10 24 4.22 10 7 m s 1 v 3070 m s 1 (o use of mv2 v GM GMm 2 ) v 3070 m s 1 F F c 67.1 N fom (b), F c mv2 so v F c m 3070 m s 1 67.1 4.22 107 300 he satellite is in eostationay obit, so must take 24 hous (86 400 s) to complete one obit v 2π 2π 4.22 107 24 60 60 3070 m s 1 v F c m he satellite is in eostationay obit so must take 24 hous (86400 s) to complete one obit (o use of v 2π ) v F c m 3070 m s 1 67.1 4.22 107 300 (allow M fo follow on eo caied fowad fo F c fom (b) ) Use of v 2π to pove v 3070 m s 1 (d) Usin F c mv2 so GmM 2 mv2 and F GmM 2 Usin v 2π : v2 4π 2 2 G 2 Combinin: 2 4π 2 3 : F F c GM so 2 4π 2 GM 3 o find the mass of the Moon: M 4π 2 3 G 2 4π 2 (1.79 10 6 ) 3 M 6.67 10 11 (6.78 10 3 ) 7.38 2 1022 k Uses F, F c and v 2π to pove 2 3. to attempt Uses F, F c and v 2π 2 3. to pove Uses F, F c and v 2π to pove 2 3. AND Calculates the mass of the moon, coectly, as bein 7.38 10 22 k
NCEA Level 3 Physics (91524) 2015 pae 3 of 9 Not Achieved Achievement Achievement with Meit Achievement with Excellence NØ N1 N2 A3 A4 M5 M6 E7 E8 No esponse; no elevant Vey little Achievement Some evidence at the Achievement level, but most is at the Not Achieved level. Most Some evidence is at the Meit level. Meit level. Evidence is povided fo most tasks. he evidence at the Excellence level may have mino eos, o the evidence is weak. Evidence is povided fo most tasks and the evidence at the Excellence level is accuate. No esponse; no elevant 1A 2A 1M 3A 1A + 1M 4A 1A + E 2A + 1M 2M 1A + 2M M + E A + M + E- 3A + E A + M + E
NCEA Level 3 Physics (91524) 2015 pae 4 of 9 Q Evidence Achievement Achievement with Meit Achievement with Excellence WO (a) he passene and the bathoom scales ae fallin at the same ate, so thee ae no contact foces between them. Accept suppot/nomal foces/eaction foce and fee fallin. Coect desciption. (b)(i) a 1.54 10 6 y, y A and 2 1.54 10 6 a max A 2 1.54 10 6 6.38 10 6 9.83 m s 2 Maximum acceleation at Eath s suface is 9.81 m s 2. Use of suitable equation e.. v A 2 sint Maximum acceleation at Eath s suface is. a A 2 1.54 10 6 6.38 10 6 9.83 m s 2 Maximum acceleation at Eath s suface is 9.81 m s 2 (b)(ii) 1.54 10 6 ads -1 A 6.38 10 6 1.24 10 3 7910 m s 1. 2, A., A Use of suitable equation e.. v Acost A. v A 6.38 10 6 1.24 10 3 7910 m s 1 A. 9.81 6.38 10 6 7910 m s 1 9.81 6.38 10 6 7910 m s 1 (c) he acceleation o estoin foce is in the opposite diection to the displacement (hence the neative sin) (y) / acts towads the equilibium position. he acceleation o estoin foce is popotional to the displacement (y). Refeence to a 2 y F ky One of diection o popotionality Complete explanation of how the equation iven shows that the elevato is undeoin simple hamonic motion.
NCEA Level 3 Physics (91524) 2015 pae 5 of 9 (d) f 1 and 2π f and 2 1.54 10 6 so 2π 2π 1.54 10 6 5063 s 84 minutes And jouney will take half of one time peiod so the time 42 minutes. 2 2π 2π, 2π 5063 s 84 minutes, A 6.38 106 9.81 Combination of f 1 and 2π f to et 2π 1.54 10 6 Combination of 2π to et 2π and Incoect answe but shows half the ime peiod. Combination of f 1 and 2π f to et 2π AND 1.54 10 6 to et 5063 s (84 minutes). Combination of 2π 2π to et 2π 5063 s 84 minutes 6.38 106 9.81 and Combination of f 1 and 2π f to et 2π Use of 2π and 2 1.54 10 6 to et 5063 s (84 minutes) he jouney time is 42 minutes (half the ime peiod). Combination of and 2π 2π to et 2π 6.38 106 9.81 And jouney will take half of one time peiod so the time 42 minutes. 5063 s 84 minutes a 1.54 10 6 y, y A and 2 1.54 10 6 1.24 10 3 Y ASint A Asint Y ASint A Asint so t π 2 t π 2 a 1.54 10 6 y, y A and 2 1.54 10 6 1.24 10 3 Y ASint A Asint he jouney time is 42 minutes (half the ime peiod). a 1.54 10 6 y, y A and 2 1.54 10 6 1.24 10 3 Y ASint A Asint
NCEA Level 3 Physics (91524) 2015 pae 6 of 9 so t π 2 t π 2 t 4 π 2(1.24 10 3 ) 1266 s 21 minutes 4 2 1266 2 2532 s 42 minutes so t π 2 t π 2 t 4 π 2(1.24 10 3 ) 1266 s 21 minutes 4 so t π 2 t π 2 t 4 π 2(1.24 10 3 ) 1266 s 21 minutes 4 2 1266 2 2532 s 42 minutes Not Achieved Achievement Achievement with Meit Achievement with Excellence NØ N1 N2 A3 A4 M5 M6 E7 E8 No esponse; no elevant Vey little Achievement Some evidence at the Achievement level, but most is at the Not Achieved level. Most Some Meit level. A majoity of the evidence is at the Meit level. Evidence is povided fo most tasks. he evidence at the Excellence level may have mino eos, o the evidence is weak. Evidence is povided fo most tasks and the evidence at the Excellence level is accuate. No esponse; no elevant 1A 2A 1M 3A 1A + 1M 4A 2M 2A + 1M 1A + 2M 1M + 1E 3M 1A + 1M + E 2M + E 3A + 1M + E 1A + 2M + E
NCEA Level 3 Physics (91524) 2015 pae 7 of 9 Q Evidence Achievement Achievement with Meit Achievement with Excellence HREE (a) he cente of mass acceleates towads the ound as a sinle foce (weiht) acts upon it. Linea momentum inceases due to the extenal foce (weiht), causin an incease in vetical velocity. Cente of mass acceleates downwads. Linea momentum inceases because the vetical velocity is inceasin. Cente of mass acceleates downwads. AND Linea momentum inceases due to extenal foce (weiht) causin an incease in vetical velocity. (Accept velocity is inceasin.) (Accept Momentum inceases because velocity inceases and the net (extenal) foce is not zeo.) (b) L I I 2.70 10 3 k m 2 I L 3.24 10 3 2.70 10 3 k m 2 1.20 (c) When the cat is in the ai, no net extenal toque acts on it about its cente of mass, so the anula momentum about the cat s cente of mass cannot chane. Since the font half of the cat has inceased anula momentum, the ea of the cat must incease anula momentum by the same amount but in the opposite diection in ode to maintain a total anula momentum of zeo. No extenal toques act. L ea L font No extenal toques act so total anula momentum must be conseved so ea half of cat must otate but in the opposite diection.
NCEA Level 3 Physics (91524) 2015 pae 8 of 9 (d) L ea + L font 0 so L ea L font 3.24 10 3 If the fallin cat pulls in its font les, the cat can decease its otational inetia / moment of inetia by chanin its mass distibution. If the fallin cat stetches out its back les, the cat can incease its otational inetia / moment of inetia by chanin its mass distibution. By chanin its otational inetia / moment of inetia, the cat can chane the speed at which it otates. Since the anula momentum of each half of its body is a constant. he cat otates moe quicky at the font of its body than at the back. L ea L font I ea ea I font font Since I m 2, I 2 ea font 2 font 2 ea ea 2 font font 2 ea 0.062 1.20 0.122 0.300 ad s 1 L ea 3.24 10 3 k m 2 s 1 he cat can chane its mass distibution Explains that the cat can chane the otational inetia of the font and back pats of its body independently Accept inetia in place of otational inetia. Explains that the cat can chane the otational inetia of the font and back pats of its body independently. uckin in the les distibutes moe of the cat s mass close to the axis of otation Stetchin out the les distibutes moe of the cat s mass futhe fom the axis of otation. Explains that the cat can chane the speed at which diffeent pats of its body otate by chanin the mass distibution. Accept inetia in place of otational inetia. Radius smalle is acceptable fo mass close to the cente/axis. Fo (M), the candidate needs to have any two of the above thee. Explains that the cat can chane the otational inetia of the font and back pats of its body independently. uckin in the les distibutes moe of the cat s mass close to the axis of otation so is quicke vice vesa (i.e. stetchin out the les distibutes moe of the cat s mass futhe fom the axis of otation so is slowe) Calculates ea 0. 300 ad s 1 Accept inetia in place of otational inetia. Radius smalle is acceptable fo mass close to the cente/axis. Fo Excellence points (E), the candidate needs to have all thee bullet points. Fo (E ), the candidate needs to have any two of the above thee.
NCEA Level 3 Physics (91524) 2015 pae 9 of 9 Not Achieved Achievement Achievement with Meit Achievement with Excellence NØ N1 N2 A3 A4 M5 M6 E7 E8 No esponse; no elevant Vey little Achievement Some evidence at the Achievement level, but most is at the Not Achieved level. Most Some evidence is at the Meit level. Meit level. Evidence is povided fo most tasks. he evidence at the Excellence level may have mino eos, o the evidence is weak. Evidence is povided fo most tasks and the evidence at the Excellence level is accuate. No esponse; no elevant A1 2A 1M 3A 1A + 1M 4A 2A + 1M 2M M + E 2A + 2M 1A + 1M + E 2A + 1M + E- 2M + E 2A + 1M + E Note: E- and E only applies to the E7 and E8 decision. Cut Scoes Not Achieved Achievement Achievement with Meit Achievement with Excellence 0 6 7 12 13 18 19 24