but answer in range (seconds) (inclusive) gains 2 marks but 2 (seconds) gains 2 marks 4

Transcription

1 Physics P2 Higher Mark Scheme Part 2 M. (a) ordinary cell has higher voltage (normally / at start) or ordinary cell.v nicad.2v (normally / at start) voltage of ordinary cell falls more slowly (accept ordinary cell lasts longer) but as above with relevant quantification e.g. falls to zero in 60 seconds compared to 6 seconds or nicad falls to zero 0 times as fast (b) (i) answer in range 2-4 (seconds) (inclusive) but answer in range (seconds) (inclusive) 2 (seconds) but 2 (seconds) 4 (c) resistance of the lamp / filament changes / increases but resistance of the lamp / filament decreases because the temperature of the filament falls / filament cools [0] Page

2 M2. (i) (fast moving) electrons (from the nucleus) (allow negatively charged particles) protactinium has one neutron fewer protactinium has one proton more (credit has different numbers of neutrons / protons with one mark) each 2 [] M. (a) indication (in writing or on graph) of finding point where radiation is halved (e.g. to 24 [from an initial 48]) and relating to the time difference between the two points but * (*i.e. in this range, including extremes) units billions of years (b) ¾ or 75% [allow ecf from (a)] (c) (i) idea that the intermediate nuclides are relatively short-lived idea that ¼ has decayed or ¾ remains Page 2

3 but read graph for radiation level of 6 (stated or shown on graph itself) but.6-.8* (billion years) (* i.e. in this range, including extremes) gains marks [8] M4. (a) idea that balanced by friction force* / pushing force equals friction force (*note balanced by unspecified force) or specification of relevant force but no reference to balancing in both (a) and (b) overall (b) balanced by upwards force of table* (c) makes it (slightly) warm / hot or wears it away (slightly) / damages surface [] M5. ideas that formed from dust/gases pulled together by gravity massive so very large gravitational forces (pulling inwards) Page

4 hydrogen helium / fusion releases energy [not fission or just nuclear ] high temperature creates high pressure (pushing outwards) long period when forces balance then expands red giant / red star then contracts to (dense) white dwarf / white star [credit if massive enough / more massive than sun, red giant supernova (very dense) neutron star but do not accept w.r.t. Sun itself] [The whole of the (non bracketed part of) each idea must be present in some appropriate for in of words for each mark to be credited. To gain more than a single mark ideas must also be in correct sequence and/or appropriately related.] any six mark each [6] M6. (a) acceleration = or but 2.5 do not penalise if both of these present but change in omitted from formula unit m/s 2 or metres per second squared or metres per second per second or ms * (b) evidence of using area under graph or distance average speed time or Page 4

5 0 4 but 20 units metres / m 2 * (c) force = mass acceleration or but 875 *NB Correct unit to be credited even if numerical answer wrong or absent. 2 [8] M7. (a) evidence of but 490 but 4900 gains marks units cm for further mark 4 Page 5

6 (b) some of radioactive solution gets into cells/body organs some of radioactive solution gets into urine (in the kidney) the radioactive solution becomes less radioactive during the test variability in readings in any order each (c) ideas that won t lose (too) much radioactivity during the test won t stay radioactive/harm cells for too long after test is over each 2 [9] ## (a) [Accept He 2+ for α] each 4 (b) [Accept β for e] each Page 6

7 4 (c) (i) beta/ β alpha/ α alpha/ α beta/ β beta/ β but alpha/ α alpha/ α beta/ β [i.e. consistent for ; consistent and correct for 2] 2 ideas that many thorium atoms because they take so long to decay* (many lead atoms because) the thorium has been decaying for so long/for billions of years or (because) the rock is so/very/billions of years of years old many lead atoms because this is the stable end product [of the decay series] few atoms of other isotopes because they decay so quickly* [*N.B. credit answers in terms of half-life] any three each [] ## (a) ideas that greater speed means more kinetic energy but any evidence of the formula ½ mv 2 but making the case that kinetic energy depends on the speed squared gains marks or that 2 2 = 4 (b) (i) any evidence of concept of momentum or mass speed (or velocity) in words or figures e.g or but correct values for momentum of lorry and car i.e. 90 and 20 [ignore units] Page 7

8 but initial momentum correctly calculated 70 or gains marks THEN evidence when calculating final speed of idea that momentum is conserved use of combined mass each gain mark but 7 [or 0. figure for initial momentum] (NB direction not required) gains marks 6 kinetic energy is lost [credit (some kinetic) energy transferred as heat/sound] [NB Accept only answers in terms of energy as required by the question] [0] M0. (a) it use E = mc 2 mass in kg i.e each but gains marks evidence of Page 8

9 mass in kg (i.e or 0.7/00000) each squaring the speed of light but 6. 0 (credit alternative ways of stating this) gains marks units J/joule for further mark (N.B credit kj, MJ, GJ but check power of 0 for full credit) 4 (b) (i) idea that the bigger the mass the shorter the life but idea that decrease in life is much more than proportional to increase in mass or more than proportional to mass 2 2 ideas that: greater mass means greater core temperature/pressure greater core temperature/pressure means greater rate of fusion increase in mass produces a proportionally much greater increase in the rate of fusion each [9] M. (a) any evidence of: momentum = mass velocity (words, symbols or numbers) appropriate re-arrangement mass as 0.05kg each but 800 gains 4 marks 4 Page 9

10 (b) (i) any reference to friction with air/air resistance but idea that friction with air/air resistance is high (at high speed) 2 any evidence of: k.e. v 2 or k.e. = ½ mv 2 final k.e. initial k.e. either initial or final k.e. correctly calculated (i.e. 6000; 0240) each but (0.8) 2 gains marks but 64%(credit 0.64) gains 4 marks (also credit e.c.f) 4 [0] M2. (a) evidence of conclusion or 4.0 each gain mark based on use of data that there is a (very small) loss of mass or but a loss of mass of for every helium atom or 0.69%/0.7% gains marks (b) idea that loss of mass results in release of energy but small loss of mass results in huge energy release 2 [5] Page 0

11 M. (a) any two from (risk of) cutting (through the) cable accept cutting the wire grass may be wet or it may rain wires may be loose (because cable experiences a lot of movement) accept cable may be loose (risk of) touching exposed part(s) 2 (b) some current will go through (the rest of) the lawnmower / the user / to earth do not credit any reference to the electromagnet (c) (i) charge = current time or any transposed version accept Q = I t or any transposed version accept C = A s or coulombs = amperes seconds or any transposed version or but only if subsequently used correctly EITHER 200 microcoulombs / μc or.2 millicoulombs / mc or coulombs /C OR correct arithmetic either converting milliamps to amps and milliseconds to seconds Page

12 or correct multiplication unit given as coulombs /C or millicoulombs / mc or microcoulombs / μc example : charge = 0 40 = 200 millicoulombs should be credited with 2 marks [7] M4. (i) EITHER 0000 (2) joules/j () or 0 kilojoules/kj OR power time = energy time = 20 (seconds) vibration (of the food processor / some part of the food processor / the food) [4] M5. (a) Formula mark P = V I accept P = VI or W = V 5 A or any transformation Substitution mark I = Calculation mark.9 accept.9 or.9 or 4 for three marks with no working Page 2

13 (b) = = 9.6 accept 9.57 to 9.6 or 0 for both marks with no working 2 (c) = = accept 0.8 or 0.8 for both marks with no working (d) any one from use less energy (to cook something) accept fewer energy losses or use less electricity cook faster do not credit a cost argument about buying two different ovens [8] M6. (a) (i) work = force distance or any correctly transposed version e.g. force = or in correct units throughout e.g. J = N m or in acceptable abbreviations e.g. W = f d do not credit W = Nm or any other ambiguous or unclear response do not credit unless subsequent calculation shows understanding Page

14 EITHER.7 (m) 2 OR (iii) (distance =) 2000 J unit required (b) EITHER 20 OR speed 2 = or speed 2 = 600 or speed 2 = 400 metres per second or m/s or speed 2 = KE mass (c) any three from deceleration (would be) (very) great or rate of change of speed / velocity would be (very) great (because) F = ma or (because) force is proportional to deceleration / (negative) acceleration (so the) force (on Susan / the rope) would be (very) great do not credit she would be hurt do not credit just the rope could snap the rope may exceed its elastic limit [0] Page 4

15 M7. (a) (i) P = V or equivalent credit a triangle if part correctly uses the relationship credit power = volts amps or watts V A do not accept C for current (P = 20 0 =) 200 credit 2. W or J/s kw (b) (i) 5 A credit A or amps any three from earth any short (to the metal tank) causes fuse to blow fuse is in the live wire to prevent damage to the heater credit to stop the current (c) (i) V = I R or equivalent credit a triangle if part correctly uses the relationship (20 = 0 R =) 2 ohms or Ω Page 5

16 2 [0] M8. (a) F 50 cm on first part of graph tolerance + or cm (b) S at the far right credit anywhere to right of last trough (c) M on any two tops of peaks or bottoms of troughs both are required for the mark M needs to be central to the trough or peak, except if F is in the way in one case [] M9. (i) either 20 C or 260 (joules of energy transferred) unit not required 20 coulomb(s) C allow J/V either 0.7 A or Page 6

17 charge = current time or 20* = current 00 or Q = It or* same as candidate s answer to part (a)(i) provided correct unit given in part (a)(i) or* as follows from above current = 0.7* amp(s) or A [6] M20. (a) either gravity due to mass of the Earth or (the) interaction / attraction between the () mass of the block and the mass of the Earth () (b) (i) 4.5 N unit required accept equal to weight (lifted) do not credit..mass.. the forces are balanced accept because the block is not accelerating accept because the block is moving at a steady speed (in a straight line) accept because the block s velocity is constant (c) (i) either Page 7

18 4.05 J or work (done) = force (applied) distance (moved in the direction of the force) or work = note = is not an equation = 4.05 joules or J or newton metres 405 J will be a common answer it gets () (for the unit) if correct equation is not shown but (2) otherwise , or variations on this theme, get () (for the unit) at most 4.05 J or same as the answer to (c) (i) provided that the same unit for energy is shown in both cases (d) 4.6 accept 4, 4.2, 4.7, 4.6 [0] M2. any one of * between (stage) 2 and (stage) * (in) the main sequence * (in) the main stable period * (it is a) yellow dwarf [] Page 8

19 M22. (a) sensible scales full use of y axis completely accurate plotting a smooth curve going through all bar one of the points do not accept a dot-to-dot graph if two parts shown for curves accept the more correct at least one line or a clear mark showing how to obtain the half life from the graph and obtaining between and 5 at the bottom of the page cross or ticks in the order of the mark scheme (b) (i) to let the beta particles get through accept must be there to let the radiation through or if thick they may be stopped alpha particles would be stopped by the glass or cannot penetrate glass do not accept alphas are weak (c) (i) it will give more counts per minute for a small quantity or it does not last so long so may not be as dangerous accept answers in terms of 5 years assume it refers appropriately it will not be there long enough to act as a tracer or it could cause radiation damage as all its activity will be in the first place it enters the system accept answer in terms of 5 seconds accept not there long enough to work assume it refers appropriately [8] Page 9

20 M2. (a) (i) power voltage = current or =.6.7 or 2 2 marks for correct answer mark for resistance = voltage current (efc here) 20.5 or or 20.6 or 2 2 marks for correct answer ohms or Ω do not credit R (b) marks only available for division of power = marks for correct answer accept 5670 [7] M24. (a).25 accept. or.2 Page 20

21 (b) plotted at. 5.7, across on the second from.2, up between first and second line sketch curve steeper near 0.64 s fairly smooth curve bending to become pretty well horizontal at.6,.25 (c) (i).68 or.7 working is 2(l ) = 2.5 m unit required consequential marking applies here (d) X at 0.64 s, 0 m it is in contact with the floor or the ball changes direction or the downward force is balanced by the reaction of the floor accept the ball is hitting the floor do not credit it has hit the floor X 2 at.6 s,.25m it is at the top of its bounce accept the ball changes direction or has run out of KE 2 [8] M25. (a) Page 2

22 one mark for each symbol allow more than 2 cells joined max. 2 marks if symbols incorrectly allow rheostat arrow in either direction (b) current will decrease since resistance greater [5] M26. (a) materials produced when earlier stars exploded accept the Sun is a second generation star accept formed from nebulae (b) Quality of written communication: mark for correct sequencing balanced forces expansion contraction / explosion any five from gravity pulling matter together accept idea that a star is very massive so its force of gravity is very strong high temperatures that create expansion forces nuclear fusion releases energy that causes the very high temperatures these forces balance star expands greatly since expansion is greater than gravity accept fuel runs out forms a red giant give no further marks if red giant white dwarf, red dwarf Page 22

23 etc collapses inwards and explodes outwards called a supernova neutron star may form leaves a small, dense object (a black hole) accept nothing can escape from it 5 [7] M kg 4 if answer incorrect then kinetic energy = mv 2 or accept indication by correct substitution accept 900 accept m = or indication by correct substitution for mark [5] M28. neutron becomes proton / neutron emits electron / neutron emits beta particle gains proton neutral [] Page 2

24 M29. (i) (strontium-90) beta rays partly absorbed by aluminium accept gamma rays not absorbed and alpha all absorbed if phosphorus -2 then one mark max for beta ray explanation long half life means it can be used for a long time (technetium-99) (gamma) rays will pass out of body / less likely to be absorbed accept (gamma) less damaging or alpha / beta will damage cells if cobalt -60 then one mark max for gamma ray explanation short half life means it will not affect body over a long period [4] M0. (a) (i) two protons 2 neutrons if neither point gained allow mark for helium nucleus electron (b) neutron splits (to form proton and electron) [4] Page 24

25 M. Quality of written communication: One mark for using correct scientific sequence : gravity fusion balance any four from (dust and gas) pulled together by gravity (star formed when) it is hot enough accept (as mass is pulled together) it gets very hot hydrogen (and helium) nuclei fuse (these nuclear fusion reactions) release the energy / heat / light (which is radiated by stars) energy causes expansion gravitational pull is balanced by the expansion (force) 4 [5] M correct with no working = if answer incorrect, allow: mark for K.E. = mass speed 2 2 marks for N.B. correct answer with the incorrectly recalled relationship weight speed 2 = 2 marks [] M Page 25

26 correct answer with no working = if answer incorrect, allow mark for force = mass acceleration 20 0 = 2 force / weight = mass gravity is neutral N.B. no marks for correct answers with incorrectly recalled relationship [] M4. (i) 7 or 8 correct data extracted from graph e.g. takes 8 days to drop from 50 to 25 allow appropriate annotation of graph long enough to destroy cancer cells do not accept dangerous unqualified but short enough to minimise damage to surrounding tissues [4] M5. (i) 7 or 8 correct data extracted from graph e.g. takes 8 days to drop from 50 to 25 allow appropriate annotation of graph long enough to destroy cancer cells do not accept dangerous unqualified but short enough to minimise damage to surrounding tissues [4] Page 26

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