Markscheme May 2017 Physics Higher level Paper 3

Transcription

1 M7/4/PHYSI/HP/ENG/TZ/XX/M Markscheme May 07 Physics Higher level Paper pages

2 M7/4/PHYSI/HP/ENG/TZ/XX/M This markscheme is the property of the International Baccalaureate and must not e reproduced or distriuted to any other person without the authorization of the IB Gloal Centre, Cardiff.

3 M7/4/PHYSI/HP/ENG/TZ/XX/M Section A a in order to keep the temperature constant in order to allow the system to reach thermal equilirium with the surroundings/owtte Accept answers in terms of pressure or volume changes only if clearly related to reaching thermal equilirium max with the surroundings. c d recognizes as gradient calculates in range to Pa m V H thus ideal gas law gives p H so graph should e «a straight line through origin,» as oserved A n = OR correct sustitution of one point from the graph RT n = = Award [ max] if POT error in. Allow any correct SI unit, eg kg s -. Answer must e to or SF. Award [] for a ald correct answer. Allow ECF from ().

4 4 M7/4/PHYSI/HP/ENG/TZ/XX/M e very large means very small volumes / very high pressures H at very small volumes the ideal gas does not apply OR at very small volumes some of the assumptions of the kinetic theory of gases do not hold

5 5 M7/4/PHYSI/HP/ENG/TZ/XX/M a 4π.60 g = = L T g = g( + ) = « =» L T OR.0 % For the first marking point answer must e given to at least dp. Accept calculations ased on gmax = gmin = gmax gmin = hence g = (9.8 ± 0.) «ms» OR = g 0. «ms» T.0 T = 0 θ max = Accept answer from interval 0 to 4.

6 6 M7/4/PHYSI/HP/ENG/TZ/XX/M Section B Option A Relativity a a set of coordinate axes and clocks used to measure the position «in space/time of an oject at a particular time» OR a coordinate system to measure x,y,z,and t / OWTTE i magnetic only there is a current ut no «net» charge «in the wire» ii electric only P is stationary so experiences no magnetic force relativistic contraction will increase the density of protons in the wire

7 7 M7/4/PHYSI/HP/ENG/TZ/XX/M 4 a ΔtP / oserver sitting in the train c t γ = t = «=»=. 0.0 Q P to give v = 0.95c γ =.5 «length of train according Q» = 5/.5 «giving 00 m» d i Award [] for one gradient correct and another approximately correct. axes drawn with correct gradients of 5 for ct and 0.6 for x

8 8 M7/4/PHYSI/HP/ENG/TZ/XX/M 4 d ii lines parallel to the x axis and passing through B and F intersections on the ct axis at B and F shown light at the front of the train must have een turned on first d iii t = s Allow ECF for gamma from (c). d iv according to P: ( ) according to Q: ( ) = = 0000 e u = c = 0.9c

9 9 M7/4/PHYSI/HP/ENG/TZ/XX/M 5 a γ =.96 E = ( γ ) mc = 900 «Me V» k pd 900«MV» 0 Award [ max] if Energy and Potential difference are not clearly distinguished, eg y the unit. energy of proton = γ mc = 88 «Me V» total energy availale = energy of proton + energy of antiproton = = 676 «MeV» momentum of a one photon = Total energy / c = 88 «Me Vc» 6 a 9 E f = «=» = « Hz» 4 h g h f f = 8550 «Hz» c «as the photon moves away from the Earth,» it has to spend energy to overcome the gravitational field since E = h f, the detected frequency would e lower «than the emitted frequency»

10 0 M7/4/PHYSI/HP/ENG/TZ/XX/M Option B Engineering physics 7 a i M vr a ii evidence of use of: M L = I ω = ( MR + R ) ω a iii evidence of use of conservation of angular momentum, v «rearranging to get ω =» 4R MvR 4 = MR ω a iv Mv initial KE = 6 Mv final KE = 4 energy loss Mv = 8

11 M7/4/PHYSI/HP/ENG/TZ/XX/M 7 i Γ 0.0 α «=» = 4 MR «to giveα = rads» Working OR answer to at least SF must e shown. ii ωi θ = «from ωf = ωi + αθ» α v. θ «= =» =.8 OR.9 «rad» R α numer of rotations «=» =.0 revolutions π

12 M7/4/PHYSI/HP/ENG/TZ/XX/M 8 a «a process in which there is» no thermal energy transferred etween the system and the surroundings A to B AND C to D c i PV T = nr T = 49 «K» c ii PV a A PB = V B P = 67 kpa B The first mark is for rearranging. The first mark is for rearranging. d i «B to C adiaatic so» 5 5 B B PV C C PV = AND PCV C = nrtc «comining to get result» It is essential to see these relations to award the mark. d ii T C 5 = PV B B V nr C (.0 0 ) T C = «(.90 0 )» = 4 «K» e the isothermal processes would have to e conducted very slowly / OWTTE

13 M7/4/PHYSI/HP/ENG/TZ/XX/M 9 a ALTERNATIVE pressure in a liquid increases with depth so pressure at ottom of ule greater than pressure at top ALTERNATIVE weight of liquid displaced greater than weight of ule weight Vρag ρa. = = = = 0 uoyancy Vρlg ρl 00 since the ratio is very small, the weight can e neglected Award [ max] if only mass of the ule is calculated and identified as negligile to mass of liquid displaced. c evidence of equating the uoyancy and the viscous force v t ( = ) = 0.6 ms «ρl π r g = 6πηrvt» 0 a the loss of energy in an oscillating system 6 Q = π 6 0. Accept calculation ased on any two correct values giving answer from interval 0 to. c the amplitude decreases at a slower rate a higher Q factor would mean that less energy is lost per cycle

14 4 M7/4/PHYSI/HP/ENG/TZ/XX/M Option C Imaging a i an image formed y extensions of rays, not rays themselves OR an image that cannot e projected on a screen a ii v = «v = cm» a iii u = 8 = 6.0 «cm» v = 4 «cm» «=» f = 8.0 «cm» f Award [ max] for answer of 4.8 cm. Minus sign required for MP. a iv line parallel to principal axis from intermediate image meeting eyepiece lens at P line from arrow of final image to P intersecting principal axis at F

15 5 M7/4/PHYSI/HP/ENG/TZ/XX/M i oject is far away so intermediate image forms at focal plane of ojective for final image at infinity oject must also e at focal point of eyepiece «hence 87.5 cm» No mark for simple addition of focal lengths without explanation. ii angular magnification = 85.0 = 4.50 angular diameter = rad c chromatic aerration is the dependence of refractive index on wavelength ut mirrors rely on reflection OR mirrors do not involve refraction «so do not suffer chromatic aerration»

16 6 M7/4/PHYSI/HP/ENG/TZ/XX/M a i longer distance without amplification signal cannot easily e interfered with less noise no cross talk higher data transfer rate max a ii infrared radiation suffers lower attenuation.4 loss = 0log = db length = «=» «km» 0.0 c a thin core means that rays follow essentially the same path / OWTTE and so waveguide (modal) dispersion is minimal / OWTTE

17 7 M7/4/PHYSI/HP/ENG/TZ/XX/M a one and tissue asor different amounts of X-rays OR one and tissue have different attenuation coefficients so oundaries and fractures are delineated in an image I I I I I I µ x I e = = e µ tx I e one 0 tissue 0 one tissue one tissue = e ( µ µ t) x. 0 (.9.) = 0.60 c i to split the energy level of protons in the ody OR to cause protons in the ody to align with the field / precess at Larmor frequency c ii to force/excite protons that are in the spin up/parallel state into a transition to the spin down/antiparallel state c iii the emitted radio frequency signal has a frequency that depends on the magnetic field with a gradient field different parts of the ody have different frequencies and so can e identified

18 8 M7/4/PHYSI/HP/ENG/TZ/XX/M Option D Astrophysics 4 a i stars fusing hydrogen «into helium» a ii 5.5 M = M (4 0 ) = 9.86M «M 40M» a iii 4 5 T 4 0 = T 4000 «K» Accept reverse working. Accept use of sustituted values into L= σ 4πR T 4. a iv 5 AU 4 0 = 4 0 d 8 d = 0 «AU» Accept use of correct values L into =. 4 π d the gravitation «pressure» is alanced y radiation «pressure» that is created y the production of energy due to fusion in the core / OWTTE Award [ max] if pressure and force is inappropriately mixed in the answer. Award [ max] for unexplained "hydrostatic equilirium is reached".

19 9 M7/4/PHYSI/HP/ENG/TZ/XX/M 4 c the Sun will evolve to ecome a red giant whereas Theta Orionis will ecome a red super giant the Sun will explode as a planetary neula whereas Theta Orionis will explode as a supernova the Sun will end up as a white dwarf whereas Theta Orionis as a neutron star/lack hole

20 0 M7/4/PHYSI/HP/ENG/TZ/XX/M 5 a i lack ody radiation / K highly isotropic / uniform throughout OR filling the universe Do not accept: CMB provides evidence for the Big Bang model. a ii.9 0 «λ =».0 «mm».8 the universe is expanding and so the wavelength of the CMB in the past was much smaller indicating a very high temperature at the eginning c i v 5 5 «z =» v = «= kms» c 5 v «d = v = = 706» 70 «Mpc» H 68 0 Award [ max] for POT error. c ii R R z =.6 R R = 0 0 R R =

21 M7/4/PHYSI/HP/ENG/TZ/XX/M 6 a a star will form out of a cloud of gas when the gravitational potential energy of the cloud exceeds the total random kinetic energy of the particles of the cloud OR the mass exceeds a critical mass for a particular radius and temperature numer of reactions is = H mass used is =.86 0 «kg» 55 c nuclear fusion reactions produce ever heavier elements depending on the mass of the star / temperature of the core the elements / nuclear reactions arrange themselves in layers, heaviest at the core lightest in the envelope

22 M7/4/PHYSI/HP/ENG/TZ/XX/M 7 a curve starting earlier, touching at now and going off to infinity i there is dark matter that does not radiate / cannot e oserved Unexplained mention of "dark matter" is not sufficient for the mark. 6 ii ρ = 0.68ρ = Λ c «kgm» energy in m is therefore J