* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download SECTION B ( 48 marks )
Anti-gravity wikipedia , lookup
Electromagnetism wikipedia , lookup
Woodward effect wikipedia , lookup
Time in physics wikipedia , lookup
Diffraction wikipedia , lookup
Thomas Young (scientist) wikipedia , lookup
Aharonov–Bohm effect wikipedia , lookup
Speed of gravity wikipedia , lookup
Lorentz force wikipedia , lookup
Faster-than-light wikipedia , lookup
Work (physics) wikipedia , lookup
Circular dichroism wikipedia , lookup
A Brief History of Time wikipedia , lookup
Electromagnet wikipedia , lookup
Electrical resistance and conductance wikipedia , lookup
Atomic theory wikipedia , lookup
Matter wave wikipedia , lookup
Wave–particle duality wikipedia , lookup
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Page : 1 CCC Hoh Fuk Tong College Mock Examination 2003 - 2004 Physics II Secondary : 7S Time allowed : 3 hrs. ( 1:00 p.m. - 4:00 p.m. ) Name : __________________________ Date : 1 / 3 / 2004 Max. marks : 93 Class : 7S Class. No. : ____ This paper must be answered in English SECTION A : Multiple Choice Questions - Answer ALL Questions SECTION B : Answer Any THREE Questions INSTRUCTIONS FOR SECTION A 1. All the answers should be marked on the Answer Sheet. 2. Note that you may only mark ONE answer to each M.C. question. Two or more answers will score NO MARKS. 3. All questions carry equal marks. No marks will be deducted for wrong answers. SECTION A ( 45 marks ) There are 45 questions in this section. Answer ALL questions. Each of the questions is followed by four suggested answers. Select the best answer in each case. Where necessary, take g = 10 m s-2 and take c to be 3 x 108 m s-1. 1. Which of the following is equivalent of a unit of energy (1) kilo-watt hour (2) electron volt (3) newton-metre. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 2. An object is thrown horizontally from the top of a cliff at a speed 20 m s-1 .What will be the speed of the object after 3 s ? A. 10 m s-1 B. 25 m s-1 C. 30 m s-1 D. 36 m s-1 . 3. Two bodies P and Q are connected by a light string A. The weights of P and Q are 6 N and 10 N respectively. P is connected to the roof by another light string B. If string B is Page : 2 cut and the bodies allowed to fall, the net force acting on P during free fall is A. B. C. D. 2N 4N 6N 16 N 4. An object of mass 3 kg is tied to another object of mass 2 kg with a string passing over a fixed smooth pulley. The weight of the pulley is negligible. When the objects move under the action of gravity, the vertical upward force acting on the axle of the pulley is A. 10 N B. 24 N C. 48 N D. 50 N 5. A motor-cycle stuntman with mass 50 kg travels around the inside of a sphere of radius 3m. What is the minimum speed he must have at the lowest point of his path so that he may remain in contact with the sphere at all times ? A. B. C. D. 3.87 m s-1 5.48 m s-1 11.0 m s-1 12.2 m s-1 6. When a constant torque T is applied to a flywheel which is accelerated from rest for 10 s, the rotational k.e. of the flywheel is E. If the constant torque T is now applied to the same flywheel for 30 s, the new rotational k.e. of the flywheel will be A. 1.5 E B. 3 E C. 4.5 E D. 9 E 7. A 0.1 kg mass suspended from a light helical spring oscillates with vertical simple harmonic motion of amplitude 2.5 cm. If the maximum kinetic energy of the mass is 3.0 x 10-3 J, its frequency of oscillation is A. 0.5 Hz Page : 3 B. 1.6 Hz C. 3.2 Hz D. 16.0 Hz 8. A body hanging on a light spring oscillates vertically between level X and Z as shown below. Its static equilibrium position is at level Y. Which of the following statements is/are correct ? (1) The acceleration of the body is zero when it is at level X. (2) The strain energy of the spring is zero when the body is at level Y. (3) The net downward force acting on the body is at its maximum when it is at level Z A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 9. Assuming the Earth to be a perfect sphere, what would be its angular velocity of rotation for an object at the equator to be weightless ( i.e. to give a spring balance reading of zero ) ? ( Radius of the Earth = 6.4 x 106 m ) A. 2.4 x 10-12 rad s-1 B. 1.6 x 10-6 rad s-1 C. 1.3 x 10-3 rad s-1 D. 8.0 x 102 rad s-1 10. The least separation between 2 points with a phase difference of /3 on a progressive wave is 0.05 m. If the velocity of the wave is 150 ms-1, the frequency of the wave is A. 200 Hz B. 300 Hz C. 500 Hz D. 600 Hz 11. A stationary sound wave vibrating in its fundamental mode is set up in an open tube . P and Q are two points at the end and the middle of the tube along its axis. Neglecting end-correction, what is the phase difference between the vibration of the air molecules at points P and Q ? A. B. C. D. 0 /4 radian /2 radian radian Page : 4 12. The figure shows an object O placed at the focus of a converging lens L. A concave mirror M is arranged on the other side of L and is 80 cm from it. If the focal length of L is 60 cm and the final image formed by this system is at infinity, what is the focal length of M ? A. B. C. D. 10 cm 20 cm 40 cm 80 cm 13. A plane transmission grating is placed at the center of a circular 0o – 360o protractor. A beam of monochromatic light is incident normally on the grating. The zeroth-order maximum occurs at a scale reading of 80o and a first-order maximum occurs at a scale reading of 55o. At what scale reading would a second-order maximum be observed ? A.148 o B. 138 o C. 130 o D. 58 o 14. Which of the following statements is/are incorrect ? (1) All standing waves are transverse waves. (2) Ultrasonic waves can be polarized. (3) Microwaves can be polarized. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 15. A hydrogen source in a laboratory emits a line spectrum with one of the lines having wavelength 656.3 nm. For a star receding from the earth at a speed of 200 km/s, what would be the wavelength of the corresponding line from the star observed on the earth ? A. 655.5 nm B. 655.9 nm C. 656.7 nm D. 657.1 nm 16. A radio produces a sound of intensity level 40 dB at a point 5 m away from it. If there are three identical radios placed and sounded together, what is the intensity level in decibel 20 m from them ? ( The radio can be regarded as a point source ) A. 10 dB B. 28 dB C. 33 dB Page : 5 D. 38 dB 17. Sunlight is scattered by air molecules in the atmosphere. Which of the following statements concerning this process is/are correct ? (1) Light is absorbed by air molecules and is then re-emitted. (2) The scattered light observed on the earth's surface is completely plane-polarized. (3) Red light is scattered more than blue light is. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 18. Two microscope glass slides are arranged so that at one end they are in contact. At the other end, they are separated by a piece of metal foil 0.020 mm thick. The slides are 10 cm long. When the slides are illuminated normally with light of wavelength 500 nm, what is the spacing of the interference fringes formed by reflection ? A. B. C. D. 0.25 mm 0.50 mm 1.25 mm 5.00 mm 19. If the fundamental frequency of a closed pipe is 300 Hz, what is the first overtone for this closed pipe ? A. 150 Hz B. 450 Hz C. 600 Hz. D. 900 Hz 20. The figure shows a pattern of electric field lines in which P, Q and R are points marked on one of the field lines with PQ=QR. If the potential at P is 0V, which of the following can give the possible potentials at Q and at R? A. B. C. D. Potential at Q -100 V -100 V +100 V +100 V Potential at R -200 V - 300 V + 200 V + 300 V 21. A charged particle is accelerated across the gap between two parallel metal plates maintained at a certain potential difference in a vacuum. Assuming there is no gravitational force, the energy acquired by the charged particle in crossing the gap depends on (1) the potential difference between the plates. Page : 6 (2) the magnitude of charge of the charged particle. (3) the width of the gap A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 22. A charged capacitor is connected across a resistor. Its voltage drops to one-third of the original value in 10 s. Find the time constant of the circuit. A. 4.1 s B. 9.1 s C. 11 s D. 25 s 23. A 4 F capacitor, which is initially charged, is discharged through a 50 resistor. The maximum current during discharge is 2 A. What is the initial energy stored inside the capacitor ? A. 2 J B. 0.2 J C. 0.1 J D. 0.02 J 24. A cell of e.m.f. 1.5 V is connected in series with a variable resistor of resistance R and an ammeter A of resistance 0. 6 . By varying R, a series of ammeter readings, I, are taken and a graph of 1/I against R is plotted. The value of the y-intercept is found to be 0.88 A-1. What is the internal resistance of the cell ? A. B. C. D. 25. 0.59 0.72 0.82 1.32 A lamp bulb is connected in series with a solenoid and an a.c. supply. Which of the following methods can decrease the brightness of the lamp bulb ? (1) Put a soft iron bar into the solenoid. (2) Increase the number of turns of the solenoid. (3) Increase the frequency of the a.c. supply, but the peak-to-peak voltage remains constant. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 26. A power station supplies electrical power to a user. The power generated by the station is 1200 kW and is transmitted at 132000 V. If the resistance of the lines connecting the power station to the user is 550 , the power available to the user is about A. 700 kW B. 1155 kW C. 1195 kW Page : 7 D. 1200 kW 27. In the above circuit, the battery has constant e.m.f. and negligible internal resistance. If switch S is closed, what would happen to the electric potential at P and at Q ? A. B. C. D. Potential at P Increased Increased Decreased Decreased Potential at Q Increased Decreased Increased Decreased 28. An additional mechanical load is applied to a rotating motor. Which of the following is/are true ? (1) The motor will decrease in speed. (2) More power will be drawn from the power supply (3) The e.m.f. induced in the rotating coil will increase. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 29. The current in a coil changes steadily from 2 A to 5 A in 75 ms so that a back e.m.f. of 1 V is induced in the coil. The self-inductance of the coil is A. 0.025 H B. 0.10 H C. 10 H D. 40 H 30. A light rectangular wire frame ABCD moves with a uniform speed to the left across a region of uniform magnetic field acting into paper. Which of the following is/are true at the instant shown in the figure ? (1) A current is flowing in the clockwise direction. (2) The electric potential at B is higher than that at C. (3) The side AD experience a magnetic force acting to the right. A. (1) only Page : 8 B. (3) only C. (1) and (2) only D. (1), (2) and (3) 31. The figure below shows an aluninium ring which floats above a coil which is carrying an alternating current. Which of the following changes alone will make the ring float at a greater height above the coil ? (1) Increase the frequency of the alternating current. (2) Make the ring thinner and with a larger radius. (3) Replace the ring with another one made of copper and of identical shape and mass. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 32. The above diagram show a rectangular current-carrying coil ABCD in a uniform magnetic field between two pole pieces. The magnetic field is perpendicular to the plane of the coil. Which of the following statements is/are correct? (1) There is a magnetic force acing on the side AB of the coil. (2) The magnetic forces acting on the coil tend to increase its area. (3). The coil will return quickly to its original vertical position when it is disturbed slightly. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 33. Two different ideal gases, A and B, are contained in two identical vessels. If the ratio of their absolute temperatures and the ratio of the root-mean-square speed of the molecules are respectively 2:1 and 3:2, the ratio of their molecular masses is A. B. C. D. 2:3 8:9 2:9 8:3 34. 1 mole of an ideal mono-atomic gas expands at a constant pressure of 105 Pa from a Page : 9 volume of 0.02 m3 to a volume 0.03 m3. The increase in internal energy of the gas is A. 500 J B. 1000 J C. 1500 J D. 2500 J 35. A uniform wire is stretched under tension. The strain in the wire depends on (1) the cross-sectional area of the wire. (2) the Young modulus of the wire. (3) the unstretched length of the wire. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 36. A sheet of aluminium is moved toward the north pole of a bar magnet. Which of the following statements is/are correct ? (1) Eddy current flows in the sheet. (2) Temperature of the sheet increases. (3) Attractive force is experienced by the magnet. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 37. The armature of a d.c. electric motor has resistance 2 . When the applied potential difference is 150 V, a current of 5 A flows. The back e.m.f. is A. 10 V B. 93 V C. 140 V D. 150 V 38. X and Y are two long solenoids having the same length and the same cross-sectional area. They are wound on the same type of core material. X has 500 turns and Y has 1 000 turns. If the self-inductance of X is 0.5 H, the self-inductance of Y is A. 0.5 H B. 0.7 H C. 1.0 H D. 2.0 H 39. In a Hall probe, the slice of semiconductor inside has 1025 charge-carriers per cubic metre. When a steady current of 0.4 A passes through the slice and a uniform magnetic field of 0.1 T applies perpendicularly to it, a Hall voltage of 17 V is set up. Find the thickness of the slice. ( Given : electronic charge = 1.6 x 10-19 C) A. B. C. D. 0.9 x 10–3 m 1.1 x 10-3 m 1.3 x 10-3 m 1.5 x 10-3 m Page : 10 40. In the above circuit, the output voltage from the operational amplifier is negative. Which of the following changes could causes the output voltage to change to positive ? (1) Increasing the value of R1. (2) Increasing the value of R3 (3) Decreasing the light intensity on the LDR. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 41. The diagram shows some energy levels ( drawn to scale ) of a certain atom. Transition X results in the emission of a photon of wavelength 600 nm. Which transition ( P to S ) would result in the emission of a photon of wavelength 300 nm ? A. Q B. R C. S D. T 42. Electron transitions occur in an atom resulting in the emission of the following light wavelengths : from level C to level A : 600 nm from level B to level A : 500 nm Which of the following statements is/are correct ? (1) Level A has a lower energy than both levels B and C. (2) Level C has a higher energy than level B. (3) The wavelength of light emitted for the transition between C and B is 100 nm. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) Page : 11 43. A radioactive sample, initially consists of only nuclide X, decays by the emission of an alpha particle to form a stable daughter nuclide Y. Which of the following quantities will decrease with time ? (1) The rate of decay of nuclide X. (2) The rate of growth of nuclide Y. (3) The rate of emission of alpha particles. A. (1) only B. (3) only C. (1) and (2) only D. (1), (2) and (3) 44. A counter is placed nearly a very weak radioactive source which has a half-life of 1 hour. The counter registers 100 counts/min at noon and 80 counts/min at 1 p.m. The expected count rate, in counts/min, at 3 p.m. on the same day is A. 50 B. 55 C. 60 D. 65 45. Given : mass of proton = 1.0073 u, mass of neutron = 1.0087 u binding energy of an alpha particle = 28.396 MeV 1 u is equivalent to 931 MeV The mass of an alpha particle is A. 3.9100u. B. 4.0015 u C. 4.0320 u. D.4.0625 u END OF SECTION A SECTION B ( 48 marks ) Answer any THREE questions from this section. Write your answers in the ANSWER BOOK provided. You should spend 1 hour and 15 minutes on this section. 1. a. State the principle of conservation of liner momentum ( 1 mark ) b. i. By considering the apparatus that can be found in a school laboratory, describe an experiment to verify the principle of conservation of linear momentum. ( 6 marks ) ii. The principle of conservation of momentum is consistent with Newton’s law of motion. By considering the collision of two objects, show that Newton’s third law can be derived from conservation of linear momentum. ( 5 marks ) c. For the following situations, briefly explain whether the total momentum is conserved and state the origin of the forces. i. The moon move in an orbit with the Earth as one of the centre of the orbit. Page : 12 ii. an particle collide with a gold atom and then rebound. ( 4 marks ) 2. a. Plane monochromatic light waves of wavelength are incident normally onto a plane transmission grating of slit separation d to produce an interference pattern. i. Using the principle of superposition describe briefly how the principal maxima are formed and deduce the formula for the angular positions of the principal maxima. ii. It is preferable to measure the wavelength of light by using a plane transmission grating rather than using a double slit. Explain briefly. ( 5 marks) b. Describe an experiment for observing the absorption spectrum of iodine using a diffraction grating. Describe the spectrum observed and account for it in terms of the quantum nature of light and atomic structure. ( 8 marks) c. Briefly explain the principles involved in identifying the elements present in the atmosphere of the sun through studying the sun’s spectrum. ( 3 marks) 3. a. A parallel-plate capacitor of capacitance C and a resistor of large resistance R are connected in series with a battery of e.m.f. having negligible internal resistance. i. Sketch graphs to show the time variation of the voltage, across the capacitor and the current in the circuit after closing switch S. Briefly explain your answer. ii. A student uses a voltmeter of resistance R to check the voltage across the capacitor and finds that the reading falls from an initial value to a final steady value /2. Briefly explain why this is so. iii With switch S closed, the plates of the capacitor are pulled apart slightly. Describe and explain the possible change(s) in the charge and the energy stored in the capacitor when the steady state is reached. ( 8 marks ) b. i. You are asked to demonstrate the change in the terminal p.d. of a supply when delivering a current. With the aid of a diagram, describe how you would carry out the experiment using a 12 V 24 W ray box lamp and some additional apparatus. Explain how the internal resistance of the supply could be estimated and state the source(s) of error. ii (I) State and discuss the significance of the order of magnitude of the internal resistance of a 5 kV E.H.T. (II) A 12 V car battery is designed to deliver a current of a hundred amperes to operate the starting motor. Explain why the headlights would dim when a car is started with the headlights on. ( 8 marks ) Page : 13 4. a. There are 2 principles involve in electromagnetic induction: the Faraday’s Law and the Lenz’s law. By considering a straight conductor moving in a uniform magnetic field, describe how these 2 principles determine the induced e.m.f. ( 4 marks ) b. i. Derive the following relation for a transformer : Np : Ns = Vp : Vs, where Np ,Ns, Vp and Vs are the number of turns of coil of the primary coil ,the secondary coil, the voltage across the primary coil and secondary coil respectively. ( 2 marks ) ii. The following is a block diagram for a transformer. When the switch K in the secondary coil is closed, describe the effects on the magnetic field line, and the energy change take place in the primary and secondary coil. ( 6 marks ) iii. Describe, with explanation, TWO methods to increase the efficiency of a transformer. ( 4 marks ) 5. a. To detect radiations, a GM tube is an useful apparatus. Briefly discuss its structure and also the working principle the GM tube. Also discuss the suitability of a GM tube for detecting particles, particles and radiation. ( 7 marks ) b. i. Sketch a graph of binding energy per nucleon against mass number and use it 92 26 U nucleus is not as stable as a 56 Fe nucleus. to explain why 235 ii. Why energy would be released when hydrogen nuclei fused to form helium nuclei ? ( 4 marks ) c. Sketch the basic structure of a nuclear power station. Explain the functions of i. the moderator, ii. the control rod, and iii. the coolant. ( 5 marks ) *** END OF PAPER ***