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CBSE Class 12 Board Exam 2018 : Physics

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ec Ne ifi w ca tio n Sp Centre Number Candidate Number ADVANCED General Certi cate of Education 2018 Physics Assessment Unit A2 1 assessing Deformation of Solids, Momentum, Thermal Physics, Circular Motion, Oscillations and Atomic and Nuclear Physics *APH11* [APH11] MONDAY 4 JUNE, AFTERNOON *APH11* TIME 2 hours. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. You must answer the questions in the spaces provided. Do not write outside the boxed area on each page or on blank pages. Complete in black ink only. Do not write with a gel pen. Answer all nine questions. INFORMATION FOR CANDIDATES The total mark for this paper is 100. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part-question. Quality of written communication will be assessed in Question 2(a). Your attention is drawn to the Data and Formulae Sheet which is inside this question paper. You may use an electronic calculator. 11137.03 *24APH1101* *24APH1101* (a) The graph in Fig. 1.1 shows how the binding energy per nucleon varies with the number of nucleons in the nucleus. Complete Fig. 1.1 by adding appropriate numerical values to the axes of the graph. [2] BE per nucleon/MeV 1 Number of nucleons in nucleus Fig. 1.1 11137.03 *24APH1102* *24APH1102* (b) Describe the principles of fission and fusion. By referring to Fig. 1.1, explain how each process can lead to energy being released. [5] [Turn over 11137.03 *24APH1103* *24APH1103* (c) (i) Equation 1.1 shows an incomplete equation to describe a fission reaction. The number of neutrons that are released has been omitted. 235 U 92 90 + 10 n 144 56 Ba + 36Kr + 1n 0 Equation 1.1 How many neutrons are released in the reaction? Number of neutrons = [1] 11137.03 *24APH1104* *24APH1104* (ii) Equation 1.2 is another example of a fission reaction. 235 U 92 139 1 + 01 n 94 40 Zr + 52Te + 3 0 n Equation 1.2 The mass of each nucleus and a neutron are given in Table 1.1. Table 1.1 Nucleus Mass / u U-235 235.0439 Zr-94 93.9063 Te-139 138.9347 n 1.0086 Calculate the number of U-235 nuclei that need to undergo fission by the reaction in Equation 1.2 to produce 1 joule of energy. Number of nuclei = [5] [Turn over 11137.03 *24APH1105* *24APH1105* 2 Quality of written communication will be assessed in part (a) of this question. (a) The control rods and the moderator are two components of a fission reactor. State a material from which each component can be made and describe how they function to produce nuclear power in a safe manner. [6] 11137.03 *24APH1106* *24APH1106* (b) The use of fossil fuels in power stations causes considerable environmental pollution due to the gases produced. The government is considering several alternative sources of power. State one advantage and one disadvantage that nuclear power has over the other alternatives to fossil fuel power. Advantage: Disadvantage: [2] [Turn over 11137.03 *24APH1107* *24APH1107* 3 (a) Gold foil was used in the historic alpha particle scattering experiment conducted by Geiger and Marsden. Gold has atomic number 79 and mass number 199. Calculate the radius of the nucleus of a gold atom. State your answer in metres. (r0 = 1.2 fm) Radius of gold atom = m [2] (b) Fig. 3.1 shows an overhead view of part of the apparatus used in the alpha particle scattering experiment. container Gold foil alpha particle source Fig. 3.1 (i) Complete Fig. 3.1 by drawing and labelling any additional apparatus that was used when Geiger and Marsden carried out the experiment. [2] (ii) Indicate, with the letter P, the position in which most alpha particles were detected in the experiment. [1] 11137.03 *24APH1108* *24APH1108* (iii) Explain why the diameter of the container can be larger than 5 cm even though the range of alpha particles in air is less than 5 cm. [1] (c) Fig. 3.2 shows the path of an alpha particle as it approaches a nucleus. Nucleus Path of alpha particle Fig. 3.2 The nucleus is replaced with one with a larger atomic number. On Fig. 3.2, sketch the new path taken by the alpha particle. [2] [Turn over 11137.03 *24APH1109* *24APH1109* 4 (a) Fig. 4.1 shows a fairground carousel where the horses move in a horizontal circle at a constant speed. IKANIMOKEN / iStock / Thinkstock Fig. 4.1 A 136 kg horse on the outside of the carousel travels in a circle of diameter 12.0 m. It takes 42 seconds for the horse to complete one full rotation. (i) Use the definition of acceleration to explain why there must be a resultant force on the horse. [3] (ii) Calculate the magnitude of the resultant force on the horse. Force = N 11137.03 *24APH1110* *24APH1110* [3] (b) On another fairground ride, the rollercoaster, a carriage and passengers of combined mass 1200 kg approaches a vertical circular section as shown in Fig. 4.2. The diameter of the circle is 38 m. 38 m Carriage Fig. 4.2 (i) What is the minimum speed of the rollercoaster carriage for the passengers to feel weightless at the top of the loop? Speed = m s 1 [2] (ii) Describe what happens to the rollercoaster carriage if the speed is less than that calculated in (i). [1] (iii) If the rollercoaster carriage has fewer passengers and therefore less mass than in (i), how will the speed at which weightlessness is experienced be affected? [1] [Turn over 11137.03 *24APH1111* *24APH1111* 5 Equation 5.1 shows the relationship between the number of radioactive nuclei N left after time t. is the decay constant and N0 is the initial number of radioactive nuclei. N = N0 e t Equation 5.1 One isotope of copper, Cu-62, can be used for medical imaging. The isotope is injected into the bloodstream and then a scan is carried out to detect the gamma rays emitted. (a) Fig. 5.1 shows a graph of the natural logarithm, Ln, of the percentage of radioactive Cu-62 nuclei remaining with time. Ln (Percentage of Cu-62 nuclei remaining) 5.0 4.5 4.0 3.5 3.0 2.5 0 5 10 15 20 Time / minutes Fig. 5.1 11137.03 *24APH1112* *24APH1112* 25 (i) What is meant by the half-life of a radioactive source and why is it important to consider the half-life when a source is used for medical imaging? [3] (ii) Use Fig. 5.1 to calculate the half-life of Cu-62. Half-life = minutes [3] (b) After two hours the activity of the source has dropped to 0.46 Bq. Calculate the initial activity of the source. Initial Activity = Bq [2] [Turn over 11137.03 *24APH1113* *24APH1113* 6 The Young modulus is an important property of the material from which contact lenses are made. Comfortable wearing of a lens is achieved using a more flexible contact lens that drapes easily over the cornea, but a high degree of flexibility can be a disadvantage when trying to achieve optimum vision. The Young modulus of two types of contact lens is shown in Table 6.1. Table 6.1 Contact Lens Young modulus / MPa Type 1 1.1 Type 2 0.49 (a) Which contact lens would be most comfortable for the user? Explain your answer. [1] (b) To find a value for the Young modulus of a lens material, lenses made from the same material with powers ranging from 8.0 D to +4.0 D were tested. (i) What was the range of focal lengths of the lenses tested in centimetres? Focal lengths range from to 11137.03 *24APH1114* *24APH1114* cm [3] (ii) Complete Table 6.2 for lenses with positive and negative power. Table 6.2 Power Defect in vision that the lens is used to correct Type of lens negative positive [4] (iii) In the test, a sample of the lens material that had a width of 2.5 mm and length of 12.0 mm, as shown in Fig. 6.1, was used. The Young modulus of one of the lenses tested was found to be 1.5 MPa. A force F of 4.2 mN in the direction shown produced a strain of 0.04. F 2.5 mm t 12.0 mm Fig. 6.1 Calculate the thickness t of the sample. Thickness = m [5] [Turn over 11137.03 *24APH1115* *24APH1115* 7 (a) Describe an experiment to determine the specific heat capacity of a metal block. Include in your answer: a diagram of the apparatus used that will ensure an accurate result, the electrical circuit, the measurements taken, how the specific heat capacity is determined from the measurements. 11137.03 *24APH1116* *24APH1116* [8] (b) A kettle with a 2700 W heating element is used to boil 750 cm3 of water. The water is initially at a temperature of 18 C. Calculate the time taken for the water to boil if the heating element has an efficiency of 75%. The specific heat capacity of water is 4.187 J g 1 C 1 and its density is 1 g cm 3. Time = s [6] [Turn over 11137.03 *24APH1117* *24APH1117* 8 A 0.25 kg mass on the end of a spring is pulled down a distance of 3 cm below equilibrium position and released so that it oscillates with simple harmonic motion. A graph of how the displacement of the mass varies with time is shown in Fig. 8.1. 0.04 0.03 Displacement /m 0.02 0.01 0 0 0.5 1.0 1.5 2.0 0.01 2.5 Time / s 3.0 0.02 0.03 0.04 Fig. 8.1 (a) (i) Explain what is meant by simple harmonic motion. [2] 11137.03 *24APH1118* *24APH1118* (ii) Calculate the displacement of the mass at a time of 12.5 seconds and state whether the mass is above or below the equilibrium position at this time. Displacement = m Position relative to equilibrium position = [6] (iii) Calculate the maximum strain energy stored in the spring. Energy = J [4] [Turn over 11137.03 *24APH1119* *24APH1119* (b) Describe how the maximum velocity of the mass could be determined from Fig. 8.1. [3] (c) (i) Describe how the mass on the spring could be forced to resonate. [1] (ii) How can you tell that the mass on the spring is resonating? [1] 11137.03 *24APH1120* *24APH1120* BLANK PAGE DO NOT WRITE ON THIS PAGE (Questions continue overleaf) [Turn over 11137.03 *24APH1121* *24APH1121* 9 (a) (i) What is the difference between the internal energy of a real gas and the internal energy of an ideal gas? [2] (ii) For a real gas to behave more like an ideal gas how should the pressure of the gas be adjusted? [1] (b) Fig. 9.1 shows an airship with an envelope containing helium gas at a pressure of 1.03 105 Pa. envelope ni / iStock / Thinkstock Fig. 9.1 11137.03 *24APH1122* *24APH1122* (i) The envelope of the airship has a volume of 8230 m3. If the temperature of the gas is 14 C, calculate the mass of helium in the envelope of the airship. The molar mass of helium = 4.003 10 3 kg mol 1. Mass of helium = kg [3] (ii) Calculate the root mean square speed of the helium gas atoms in the envelope of the airship. Root mean square speed = m s 1 THIS IS THE END OF THE QUESTION PAPER 11137.03 *24APH1123* *24APH1123* [3] DO NOT WRITE ON THIS PAGE For Examiner s use only Question Marks Number 1 2 3 4 5 6 7 8 9 Total Marks Examiner Number Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. 236901 *24APH1124* *24APH1124* Sp N ec e ifi w ca tio n ADVANCED General Certificate of Education Physics Assessment Units A2 1 and A2 2 [APH11/APH21] DATA AND FORMULAE SHEET FOR USE FROM 2018 ONWARDS 12159.02 Data and Formulae Sheet for A2 1 and A2 2 Values of constants speed of light in a vacuum permittivity of a vacuum c = 3.00 108 m s 1 0 = 8.85 10 12 F m 1 1 = 8.99 109 F 1 m 4 0 elementary charge the Planck constant (unified) atomic mass unit mass of electron mass of proton molar gas constant the Avogadro constant the Boltzmann constant gravitational constant e = 1.60 10 19 C h = 6.63 10 34 J s 1 u = 1.66 10 27 kg me = 9.11 10 31 kg mp = 1.67 10 27 kg R = 8.31 J K 1 mol 1 NA = 6.02 1023 mol 1 k = 1.38 10 23 J K 1 G = 6.67 10 11 N m2 kg 2 acceleration of free fall on the Earth s surface electron volt the Hubble constant g = 9.81 m s 2 1 eV = 1.60 10 19 J H0 2.4 10 18 s 1 12159.02 2 Useful formulae The following equations may be useful in answering some of the questions in the examination: Mechanics conservation of energy Hooke s Law strain energy 1 1 mv 2 mu 2 = Fs 2 2 for a constant force F = kx (spring constant k) 1 1 E = Fx = kx 2 2 2 Uniform circular motion mv 2 F= r centripetal Force Simple harmonic motion x = A cos t l T = 2 g m T = 2 k displacement simple pendulum loaded spiral spring Waves 12159.02 ay d two-source interference = diffraction grating d sin = n 3 Thermal physics average kinetic energy of a molecule kinetic theory thermal energy 3 1 m Gc2H = kT 2 2 1 pV = Nm Gc2H 3 Q = mc Capacitors capacitors in series 1 1 1 1 = + + C C1 C2 C3 capacitors in parallel C = C1 + C2 + C3 time constant capacitor discharge = RC t Q = Q0e CR t CR or V = V0e or I = I0 Light lens formula t e CR 1 1 1 + = u v f Electricity 12159.02 terminal potential difference V = E Ir (e.m.f., E; Internal Resistance, r) R1Vin potential divider Vout = R1 + R2 a.c. generator E = BAN sin t 4 Nuclear Physics nuclear radius r= radioactive decay A = N, A = A0e t 0.693 t1 = 2 half-life Particles and photons Einstein s equation de Broglie equation 1 mvmax2 = hf hf0 2 h = p Astronomy red shift recession speed Hubble s law 12159.02 1 r0A 3 v z= c z= v = H0 d 5

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