• 9702 November 2012 Paper 12 Worked Solutions | A-Level Physics

Paper 12

1 B                  11 A                21 D                31 A

2 A                  12 D                22 A                32 B

3 B                  13 D                23 A                33 C

4 C                  14 D                24 D                34 C

5 B                  15 B                25 D                35 C

6 A                  16 D                26 D                36 C

7 D                  17 C                27 B                37 C

8 A                  18 C                28 C                38 B

9 C                  19 A                29 A                39 C

10 D                20 D                30 D                40 D

Notes for some specific questions:

  

2 - Ans: A. {Detailed explanations for this question is available as Solution 746 at Physics 9702 Doubts | Help Page 151 - http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-151.html}


3 - Ans: B. {Detailed explanations for this question is available as Solution 752 at Physics 9702 Doubts | Help Page 152 - http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-152.html}

5 – Ans: B. Volume: need to find cross-sectional area and length. Vernier caliper : least = about 0.05mm, used to measure comparatively larger object.

6 – Ans: A.

Variables x and y are related by the equation y = p – qx where p and q are constants.

Values of x and y are measured experimentally. The results contain a systematic error.

Which graph best represents these results?

7 - Ans: D. {Detailed explanations for this question is available as Solution 848 at Physics 9702 Doubts | Help Page 169 - http://physics-ref.blogspot.com/2015/06/physics-9702-doubts-help-page-169.html}


8 - Ans: A. {Detailed explanations for this question is available as Solution 758 at Physics 9702 Doubts | Help Page 153 - http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-153.html}



9 - Ans: C. {Detailed explanations for this question is available as Solution 233 at Physics 9702 Doubts | Help Page 37 - http://physics-ref.blogspot.com/2014/12/physics-9702-doubts-help-page-37.html}

10 – Ans: D. {Detailed explanations for this question is available as Solution 720 at Physics 9702 Doubts | Help Page 145 - http://physics-ref.blogspot.com/2015/05/physics-9702-doubts-help-page-145.html}

11 – Ans:A.  1h = 3600s. Speed in metre per second = 80000 / 3600 = 22.22ms^-1. a = gradient = (22.22 – 0) / (20 – 0) = 1.1ms^-2. (verify units)

12 – Ans: D. change in momentum = mv₂ – mv₁ = 0.5(8 – (-12)) = 10. Force = Δp/t = 10 / 0.10 = 100N. (Momentum is a vector and the change in momentum is 10 kgms^–1giving a force of 100 N.)

13 - Ans: D. {Detailed explanations for this question is available as Solution 585 at Physics 9702 Doubts | Help Page 115 - http://physics-ref.blogspot.com/2015/04/physics-9702-doubts-help-page-115.html}


14 - Ans: D. {Detailed explanations for this question is available as Solution 602 at Physics 9702 Doubts | Help Page 119 - http://physics-ref.blogspot.com/2015/04/physics-9702-doubts-help-page-119.html}

16 – Ans: D. There is no viscous force on a stationary object, so D is correct. For B and C, body sinks.

17 - Ans: C. {Detailed explanations for this question is available as Solution 1047 at Physics 9702 Doubts | Help Page 219 - http://physics-ref.blogspot.com/2015/10/physics-9702-doubts-help-page-219.html}


18 - Ans: C. {Detailed explanations for this question is available as Solution 291 at Physics 9702 Doubts | Help Page 49 - http://physics-ref.blogspot.com/2015/01/physics-9702-doubts-help-page-49.html}

19 – Ans: A. Work done = Force x distance. Force = Pressure x area = 4000Pa x 500x10^-4 m² = 200N. WD = 200 x 0.3 = 60J (take units into account)

 

20 - Ans: D. {Detailed explanations for this question is available as Solution 562 at Physics 9702 Doubts | Help Page 110 - http://physics-ref.blogspot.com/2015/04/physics-9702-doubts-help-page-110.html}


21 - Ans: D. {Detailed explanations for this question is available as Solution 831 at Physics 9702 Doubts | Help Page 166 - http://physics-ref.blogspot.com/2015/06/physics-9702-doubts-help-page-166.html}


22 - Ans: A. {Detailed explanations for this question is available as Solution 581 at Physics 9702 Doubts | Help Page 114 - http://physics-ref.blogspot.com/2015/04/physics-9702-doubts-help-page-114.html}

23 – Ans: A. Ice floats on water at 0 °C, so it is less dense than water and its molecules must be on average further apart than those in water. At a fixed temperature all the molecules, whether in ice or water, have the same average speed.

26 – Ans: D. {Detailed explanations for this question is available as Solution 794 at Physics 9702 Doubts | Help Page 160 - http://physics-ref.blogspot.com/2015/06/physics-9702-doubts-help-page-160.html}

27 – Ans: B. Young modulus of wire X is twice that of wire Y. diameter of X is half that of wire Y. Both are extended with equal strain and obey Hooke’s law. Since strain is equal and Young modulus of X is twice that of Y, stress on X is twice that on Y. Diameter of X is half that of Y, so x-area of X is ¼ area of Y.

28 - Ans: C.
The diagram shows two identical loudspeakers driven in phase by a common audio-frequency source.

29 - Ans: A. {Detailed explanations for this question is available as Solution 111 at Physics 9702 Doubts | Help Page 21 - http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-21.html}

30 – Ans: D. Monochromatic light of wavelength 690 nm passes through a diffraction grating with 300 lines per mm, producing a series of maxima on a screen.

31 – Ans: A. period, T corresponds to 2cm = 2x0.20μs = 0.4x10^-6s. Frequency, f  = 1/T = 2.5x10⁶Hz = 2.5MHz. Wavelength radio wave: 1m – 100 000km and freq: 300MHz – 3Hz (A popular incorrect answer was B, but 2.5 MHz is nowhere near the microwave region (from question, wavelength would be 120 m), (wavelength of microwave: 1mm – 1meter and freq: 300GHz – 300MHz))

33 – Ans: C. Both p and He have same charge, so deviation occur in the same direction (side). F = Eq. q of He is twice that of a proton but since its mass is 4 times that of a proton, deviation is less. E = ½ mv². v same.

34 – Ans: C. R = ρl/A. R inversely proportional A, so R is less for larger A. (A incorrect) X and Y are made from same material, so they have same resistivity (B incorrect). When two wires are connected in series, current must be the same in both. The extra resistance of X then makes its I²R term twice that for Y. emf is the same in each loop of a parallel circuit. (V=IR) For same length of wire, R of X is twice that of Y, so I in X would be half that in Y for emf to be similar.

36 – Ans: C. {Detailed explanations for this question is available as Solution 968 at Physics 9702 Doubts | Help Page 200 - http://physics-ref.blogspot.com/2015/09/physics-9702-doubts-help-page-200.html}

 

37 - Ans: C. {Detailed explanations for this question is available as Solution 447 at Physics 9702 Doubts | Help Page 86 - http://physics-ref.blogspot.com/2015/03/physics-9702-doubts-help-page-86.html}

39 - A material contains a radioactive isotope that disintegrates solely by the emission of α-particles at a rate of 100 s-1.

40 - Ans: D.
A different nucleus can be formed by bombarding a stable nucleus with an energetic α-particle.

Explanations have been provided for questions that were found to be more difficult. If you are having other doubts that have not been explained here, you may ask your questions through comments.