Markscheme May 2018 Physics Standard level Paper 3

Transcription

1 M8/4/PHYSI/SP/ENG/TZ/XX/M Markscheme May 08 Physics Standard level Paper 4 pages

2 M8/4/PHYSI/SP/ENG/TZ/XX/M This markscheme is the property of the International Baccalaureate and must not be reproduced or distributed to any other person without the authorization of the IB Global Centre, Cardiff.

3 M8/4/PHYSI/SP/ENG/TZ/XX/M Section A. a distance fallen «mm» absolute uncertainty 0.«mm» 0 «m» or. 0 «m» or.0 0 «m» Accept answers in mm or m. b s 0.64 «a» «ms» t 0.6 fractional uncertainty in distance AND fractional uncertainty in time s t total fractional uncertainty « » s t Accept working in for MP and MP 4 total absolute uncertainty 0. or 0.4 AND same number of decimal places in value and uncertainty, ie: or Final uncertainty must be the absolute uncertainty

4 4 M8/4/PHYSI/SP/ENG/TZ/XX/M. a combines the two equations to obtain result 4 «for example K ( C x) ( C x)» I P reverse engineered solution substitute K P I 4 ( C x) P into K I C x ( ) to get There are many ways to answer the question, look for a combination of two equations to obtain the third one. b i extrapolating line to cross x-axis / use of x-intercept Use C y-intercept gradient use of gradient and one point, correctly substituted in one of the formulae accept answers between.0 and 4.5 «cm» Award [ max] for negative answers (continued )

5 5 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question continued). b ii ALTERNATIVE Evidence of finding gradient using two points on the line at least 0 cm apart Gradient found in range: 5 5 or.5.5 Using 4 P to get value between K and W and POT correct Correct unit, W and answer to, or significant figures ALTERNATIVE Finds I from use of one point (x and y) on the line with y P x 6cm and C from (b)(i) to use in I or 4 ( C x) x I K KC Correct re-arrangement to get P between «W» and POT correct and Correct unit, W and answer to, or significant figures Award [ max] for an answer between 6.9W and 9.5W (POT penalized in rd marking point) Alternative is worth [ max] 4 (continued )

6 6 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question continued). c this graph will be a curve / not be a straight line OWTTE more difficult to determine value of K more difficult to determine value of C suitable mathematical argument

7 7 M8/4/PHYSI/SP/ENG/TZ/XX/M Section B Option A Relativity. a i.5c. a ii ALTERNATIVE ( ) u c c ALTERNATIVE u c ( ) 0.9c. b nothing can travel faster than the speed of light (therefore (a)(ii) is the valid answer) OWTTE

8 8 M8/4/PHYSI/SP/ENG/TZ/XX/M 4. a 0.60c «m s» 4. b ALTERNATIVE time interval in the Earth frame 90.5 minutes «in Earth frame it takes.5 minutes for ship to reach station» so distance c. 0 «m» ALTERNATIVE Distance travelled according in the spaceship frame c «m» Distance in the Earth frame « ». 0 «m» (continued )

9 9 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question 4 continued) 4. c signal will take « » 67.5 «minutes» to reach Earth «as it travels at c» signal will take «s» 8 0 total time «67.5.5» 80 minutes or.00 h or :00am 4. d i line from event E to A, upward and to left with A on ct axis (approx correct) line from event A to B, upward and to right with B on ct' axis (approx correct) both lines drawn with ruler at 45 (judge by eye) eg: (continued )

10 0 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question 4 continued) 4. d ii ALTERNATIVE «In spaceship frame» Finds the ratio OB OE approximately 4 (or by similar triangles on x or ct axes), value is hence time elapsed 4 90mins 6h «so clock time is 6:00» Alternative : Allow similar triangles using x-axis or ct-axis, such as distance from diagrams below distance (continued )

11 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question 4 continued) 4. d ii ALTERNATIVE «In Earth frame» Finds the ratio ct coordinate of B,value is ct coordinate of A approximately.5.5 h hence time elapsed 6h.5 «so clock time is 6:00» ALTERNATIVE :

12 M8/4/PHYSI/SP/ENG/TZ/XX/M 5. a quantity that is the same/constant in all inertial frames 5. b i spacetime interval «m» 5. b ii ALTERNATIVE Evidence of x t «s» c ALTERNATIVE t «s» 5. c observer B measures the proper time and this is the shortest time measured time dilation occurs «for B's journey» according to A observer B is stationary relative to the particle, observer A is not

13 M8/4/PHYSI/SP/ENG/TZ/XX/M Option B Engineering physics 6. a i an object s resistance to change in rotational motion OWTTE equivalent of mass in rotational equations 6. a ii KE rotational KE GPE v mv I r mgh 4 v 0.50 v v. «m s» 6. a iii.» 00 rad s « b i force in direction of motion so linear speed increases 6. b ii force gives rise to anticlockwise/opposing torque on OWTTE wheel so angular speed decreases

14 4 M8/4/PHYSI/SP/ENG/TZ/XX/M 7. a ALTERNATIVE V V «Using T T» V 47. (7 9) (7 ) V 5.7 «m» ALTERNATIVE «Using PV nrt» 4 8. (7 9) V. 0 V 5.6 «m» 7. b W «P V». 0 ( ) W «J» Accept J if 5 used Accept J if 5.6 used 7. c 4 U «nr T» (9 ( )) Q «U W» Accept if J used Accept if J used 5 Q.57 0 «J» (continued )

15 5 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question 7 continued) 7. d i concave curve from RHS of present line to point above LHS of present line vertical line from previous curve to the beginning p 7. d ii energy is removed from the gas and so entropy decreases temperature decreases «at constant volume (less disorder)» so entropy decreases 7. e different paradigms/ways of thinking/modelling/views allows testing in different ways laws can be applied different situations 0 0 OWTTE OWTTE V max

16 6 M8/4/PHYSI/SP/ENG/TZ/XX/M Option C Imaging 8. a i constructs ray parallel to principal axis and then to image position u 8cm and v 4cm and lens formula eg: O.0 cm I converging lens 6 «cm» Allow answers in the range of 5.6 to 6.4 cm 8. a ii m.0 8. b completes diagram with blue focal point closer to lens First marking point can be explained in words or seen on diagram blue light/rays refracted/deviated more speed of blue light is less than speed of red light different colors/wavelengths have different focal points/converge at different points

17 7 M8/4/PHYSI/SP/ENG/TZ/XX/M 9. a where the extensions of the reflected rays from the primary mirror would meet, with construction lines eg: secondary mirror X primary mirror reflecting telescope 9. b greater magnification 9. c Newtonian mount has plane/not curved «secondary» mirror «secondary» mirror at angle/45 to axis eyepiece at side/at 90 to axis mount shown is Cassegrain OWTTE Accept these marking points in diagram form max 9. d waves collected above mirror/dish waves collected at the focus of the mirror/dish waves detected by radio receiver/antenna waves converted to electrical signals max

18 8 M8/4/PHYSI/SP/ENG/TZ/XX/M 0. a.4444 sinc or sinc critical angle 86. with cladding only rays travelling nearly parallel to fibre axis are transmitted pulse broadening/dispersion will be reduced OWTTE 0. b i I.0 0 attenuation «0 log» 0 log I attenuation «db» 0. b ii loss over length of cable 0 7 «.7»so two amplifiers are sufficient 0. b iii mention of material dispersion mention that rays become separated in time 6 6 Accept log.0 for first marking point mention that ray A travels slower/arrives later than ray B (continued )

19 9 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question 0 continued) 0. c high bandwidth/data transfer rates low distortion/low noise/faithful reproduction high security Allow any other verifiable sensible advantage fast «fibre» broadband/internet max high quality optical audio medical endoscopy

20 0 M8/4/PHYSI/SP/ENG/TZ/XX/M Option D Astrophysics. a photon/fusion/radiation force/pressure balances gravitational force/pressure gives both directions correctly (outwards radiation, inwards gravity) OWTTE. b.5 «L M for main sequence». c i luminosity of P.5 «luminosity of the Sun» L Gacrux Gacrux ( ) L 4. 0 «W» L Gacrux L c ii if the star is too far then the parallax angle is too small to be measured stellar parallax is limited to closer stars OWTTE (continued )

21 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question continued). d i line or area roughly inside shape shown judge by eye Accept straight line or straight area at roughly 45. d ii P between L and 0 L on main sequence drawn (continued )

22 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question continued). d iii at 0 L, further to right than 5000 K and to the left of 500 K (see shaded region) (continued )

23 M8/4/PHYSI/SP/ENG/TZ/XX/M (Question continued). e ALTERNATIVE Main sequence to red giant planetary nebula with mass reduction/loss OWTTE for both alternatives planetary nebula with mention of remnant mass white dwarf ALTERNATIVE Main sequence to red supergiant region Supernova with mass reduction/loss Supernova with mention of remnant mass neutron star Black hole

24 4 M8/4/PHYSI/SP/ENG/TZ/XX/M. a use of gradient or any coordinate pair to find H convert Mpc to m and km to m «for example age of universe 0 v d or d H v » «s» H 0 Allow final answers between and «s» or «s». b non-accelerated/uniform rate of expansion H 0 constant over time. c 4 v z c.00 0 R z.5 R 0 R R «.5» 87 % of the present size OWTTE