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98 AL Physics/M.C./P.1 1998 Hong Kong Advanced Level Examination AL Physics Multiple Choice Question 1. 3. P 0.5 kg Two identical light springs are connected with two masses of 1.0 kg and 0.5 kg as shown. Which of the following statements is/are correct? A. (1) The tension in the upper spring is double that in the lower spring. (2) The force acting on the ceiling by the whole system is 15 N. (3) The tension in the upper spring will remain unchanged if the two masses are exchanged in position. C. 2. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) B Q Two blocks A and B of mass ratio 1:2 are placed on a horizontal frictionless surface as shown above. P and Q are horizontal forces acting on A and B respectively (with P > Q) so that the blocks move to the right with constant acceleration. Find the force acting on B by A. 1.0 kg A. B. C. D. E. A B. D. E. PQ 3 PQ 3 2( P Q) 3 2P Q 3 P 2Q 3 4. final momentum North 45 initial momentum The velocities of the longitudinal and transverse waves produced by an earthquake are 5.0 kms-1 and 9.0 kms-1 respectively. A seismograph records the arrival of the transverse waves 64 s before that of the longitudinal waves. How far away was the earthquake? The initial momentum of an object is 2 Ns in the direction of S 45 E and its final momentum is 1 Ns due east. If this change takes place in 0.5 s, the average force acting on the object during the change is A. B. C. D. E. A. B. C. D. E. 256 km 320 km 576 km 659 km 720 km 1 N due north 1 N due south 0.5 N due north 2 N due south 2 N due north 98 AL Physics/M.C./P.2 5. (1) The kinetic energy of B is four times that of A. (2) The frictional force acting on B is double that acting on A. (3) If the angular speed of the turntable gradually increases, B will slip before A. F/N 4 0 5 A. B. C. D. E. t/s The graph shows the time variation of the net force, F, acting on an object of mass 1 kg. The object is initially at rest and its subsequent motion is along a straight line. Which of the following statements is/are correct? 8. (1) The object is accelerating in the first 5 seconds. (2) The maximum speed of the object is less than 10 ms-1. (3) The final speed of the object is zero. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) A body hanging on a light spring oscillates vertically between levels X and Z as shown below. Its static equilibrium position is at level Y. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) Z Y X 6. A small object is thrown horizontally towards a vertical wall 1.2 m away. It hits the wall 0.8 m below its initial horizontal level. At what speed does the object hit the wall? (Neglect air resistance.) Which of the following statements is/are correct? (1) The accelerating 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. wall 1.2 m 0.8 m A. B. C. D. E. A. B. C. D. E. -1 2 ms 3 ms-1 4 ms-1 5 ms-1 7 ms-1 9. 7. Two small identical coins A and B are placed on a horizontal turntable which is kept rotating at a constant angular speed about a vertical axis through its centre. The distance of B from the axis of rotation is twice that of A from the axis. Which of the following statements is/are correct? (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) A mass is suspended by a light spring fixed to the ceiling. When the mass-spring system undergoes vertical oscillation freely, its frequency is f0. If the system is removed from the ceiling and forced to oscillate vertically by a periodic driving force by variable frequencies, which of the following graphs best represents the relationship between its frequency of 98 AL Physics/M.C./P.3 oscillation, f, and the applied frequency, fa? E. f A. f 0 0 f0 fa fa f0 10. Which of the following travel(s) with the speed of light in vacuum? B. f 0 (1) cathode rays (2) -rays (3) ultra violet radiation f0 fa A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 11. The displacement-time graphs of two oscillating particles P and Q are shown below. C. f Displacement P Time 0 0 f0 fa Q D. f 0 Which of the following phase relations between P and Q is correct? f0 fa 4 P leads Q by 2 P leads Q by . Q leads P by 4 Q leads P by 2 A. P leads Q by . B. . C. D. E. . . 98 AL Physics/M.C./P.4 12. A beam of red (R) light and violet (V) light strikes normally on a diffraction grating. Several orders of diffraction of the light beam are produced on each side of the central axis. The wavelength of the red light is 700 nm and that of the violet light is 400 nm. How will the second- and third- order diffracted beams of both colours appear? (The central axis is marked with a dot and the diffracted beams of other orders are not shown.) A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 14. B D i Central axis V R V R A A. medium X medium Y C V V R R B. V R R V R R V V R V R V C. D. E. 13. B A C D The above figure shows a transverse wave propagating along a string. At the instant shown, the particle D on the string is moving downward. Which of the following deductions is/are correct? (1) The wave is propagating to the left. (2) Particle B takes longer than particle A to return for the first time to the respective equilibrium positions along the dotted line. (3) Particles C and D are moving in opposite directions at the instant shown. A wave is incident on a boundary between two media X and Y at an angle of incidence i. AB represents the incident wavefront and CD the refracted wavefront. Which of the following statements is/are correct? (1) The frequency of the wave changes when passing from X to Y. (2) The end B of the wavefront travels to D at the same time as the end A travels to C. (3) When angle i increases, it is possible for the wavefront to be totally reflected at the boundary. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 15. 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 partially planepolarized. (3) Red light is scattered more than blue light is. 98 AL Physics/M.C./P.5 A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) A. B. C. D. E. 16. On the surface of the earth 3.4 108 m from the earth 1.9 108 m from the earth 0.4 108 m from the earth On the surface of the moon 18. L2 L1 L3 water In the above circuit, light bulbs L1, L2 and L3 consume power at the rate 1:1:3. If the resistance of L3 is R, the resistance of L1 is tap The above figure shows a long vertical glass tube containing water. The water level is lowered until the first resonance occurs when a vibrating tuning fork is placed at the opening of the tube. Which of the following statements is/are correct? (Neglect end corrections.) (1) The sound produced by the air column above the water has the same frequency as the tuning fork. (2) Resonance will occur again if the length of the air column above the water is increased to three times its original value. (3) Resonance will occur again if another tuning fork of twice the frequency is used. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 17. The mass ratio of the earth and the moon is 81:1 and the earth-moon separation is 3.8 108 m. At which position between the earth and the moon is the gravitational potential at a maximum? (Ignore all other planets.) A. B. C. D. E. 3R/16 R/4 3R/4 4R/9 3R 19. current/A 5.0 1.0 0 1.0 2.0 voltage/V The variation of current with the voltage applied across a device is as shown. What is the change in resistance of the device when the voltage increases from 1.0 V to 2.0 V? A. B. C. D. E. It decreases by 0.25 It increases by 0.25 It decreases by 1.50 It increases by 0.60 It decreases by 0.60 98 AL Physics/M.C./P.6 20. A. 2.0 V E S 0.8 H 0 4.0 Q B. E A coil of inductance 0.8 H is connected in series with a switch S and a cell of e.m.f. 2.0 V. The total resistance of the circuit is 4.0 . What is the initial rate of growth of the current when the switch is closed? A. B. C. D. E. 0 0 As-1 0.4 As-1 0.5 As-1 1.6 As-1 2.5 As-1 Q C. E 21. 0 10 k Q D. E 6V 5 k 2V V voltmeter, 5 k In the above circuit each cell has negligible internal resistance. The voltmeter has a resistance of 5 k. The reading on the voltmeter is A. B. C. D. E. 0V 1.0 V 1.2 V 1.5 V 2.0 V 22. Which of the following graphs shows correctly the relationship between the energy E stored in an isolated conducting sphere and the charge Q on it? 0 Q E. E 0 Q 98 AL Physics/M.C./P.7 23. E. A C V R B VR 0 24. R B. A charged capacitor C1, is connected to an uncharged capacitor C2 of larger capacitance through a resistor R as shown above. When switch S is closed, which of the following statement is INCORRECT? A. The total charges on the two capacitors remain unchanged. B. The final charge on C2 is greater than that on C1. C. The potential difference across C1 falls. D. The potential difference across the two capacitors finally becomes equal. E. The total energy stored in the two capacitors remains the same. t VR 0 S C2 VR 0 C1 t A changing voltage V is applied across AB in the circuit shown. The potential difference VAC across the capacitor is found to vary with time t as shown. Which of the following graphs shows the variation of potential difference VR across the resistor R with time t? A. t D VAC 0 VR t 25. current /A C. 5.0 VR time/ms 0 0 t 2 3 4 5 An alternating current flowing through a resistor varies with time as shown above. What is the value of the direct current that gives the same heating effect as the alternating current? D. VR 0 1 -3.0 t A. B. C. D. E. 3.9 A 4.0 A 4.1 A 4.2 A 4.3 A 98 AL Physics/M.C./P.8 26. E. T v 0 The figure shows a charged particle moving in a circle with constant speed v on a plane perpendicular to a uniform magnetic field. Which of the following graphs represents the relation between the time T for the particle to complete a circle and its speed v? 27. P r r A. T 0 current I into paper r Two long, straight parallel conducting wires, each carrying a current I, are separated by a distance r as shown. What is the magnetic field at a point P at the same distance r from both wires? (0 = permeability of free space) v B. T A. B. 0 v C. C. T D. E. 0 v 0I to the left 2r 3 0 I to the left 2r 0I to the left r 3 0 I to the right 2r 0I to the right 2r 28. D. T R 0 v C L The root-mean-square voltages across the resistor R, capacitor C and inductor L of an RCL series circuit are respectively 4 V, 1 V and 4 V. What is the phase difference between the applied voltage and the current flowing in the circuit? 98 AL Physics/M.C./P.9 A. B. C. D. E. 31. 30 37 45 53 60 -particle 29. A capacitor has a capacitance of 1 farad. Which of the following deductions must be correct? -particle The above diagram shows two -particles moving directly towards each other with the same speed. Which of the following statement is/are correct? (1) It stores 1 coulomb of charge at a potential difference of 1 volt. (2) It gains 1 joule of electrical energy when it has 1 coulomb of charge. (3) It will be fully charged in 1 second by a constant current of 1 ampere. (1) The two particles attract one another. (2) The electric potential energy of the two particles is decreasing at the instant shown. (3) The total momentum of the two particles remains constant in the subsequent motion. A. B. C. D. E. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 32. Which of the following is/are random process(es)? 30. B A N C S D The above diagram shows 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 acting on the side BC of the coil. (2) The magnetic forces acting on the coil tend to reduce its area. (3) The coil will return quickly to its original vertical position when it is disturbed slightly. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) (1) The background radiation in radioactivity. (2) The Brownian motion of smoke particles in a smoke cell. (3) The scattering of -particles by the nuclei in a piece of gold foil. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 33. The internal energy of an ideal gas always changes when (1) its volume increases. (2) it undergoes an isothermal change. (3) it is compressed in an insulating container. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 34. In which of the following cases will heat always flow away from a body X? 98 AL Physics/M.C./P.10 Force (1) X is changed from its liquid state to a solid at freezing point. (2) X is in thermal contact with another system at a lower temperature. (3) X is in thermal contact with another system which has a smaller amount of internal energy. A. B. C. D. E. 0 (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) Separation P Q The figure shows the force-separation graph for a pair of atoms in a material. Which of the following features is most closely related to the stiffness and the tensile strength of the material? 35. The root-mean-square speed of a sample of helium gas molecules, each of mass m, is c. Which of the following deductions is correct? (1) the value of the separation at P (2) the value of the separation at Q (3) the value of the slope of the graph at P (4) the value of the force at Q A. The percentage of molecules travelling at speed c is greater than at other speeds. B. Half of the molecules travel at a speed higher than c. C. All molecules travel randomly with speed c. D. The average speed of the molecules is c. E. The average kinetic energy of the molecules is ½mc2. Stiffness (1) (1) (3) (3) (4) A. B. C. D. E. Tensile strength (2) (4) (2) (4) (3) 38. screen 36. A uniform vertical steel wire is stretched by hanging a weight from its lower end. Which of the following would put a greater strain on the wire? (The Young modulus of steel is greater than that of brass.) V d filament A. B. C. D. E. 37. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) deflection Q electron gun (1) Using a steel wire of greater unstretched length. (2) Using a steel wire of greater crosssectional area. (3) Replacing the steel wire with a brass wire of the same unstretched length and cross-sectional area. P anode L In a cathode ray tube, the beam of electrons from the electron gun is deflected vertically when a p.d. is applied between the deflection plates, P and Q, of length L and separation d. Which of the following changes will increase the deflection of the beam for a given p.d. across the deflection plates? (1) Reducing the p.d. V between the filament and the anode. (2) Reducing the separation d between the deflection plates. (3) Reducing the length L of the deflection plates. 98 AL Physics/M.C./P.11 A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) A. B. C. D. E. 39. 41. The activity of a sample of radioactive isotopes decreases to 1/3 of its initial value in 12 s. How much more time would be required for the activity to decrease to 1/9 of its initial value? S V In the above circuit, the resistors are identical, the battery has negligible internal resistance and the voltmeter draws negligible current. What are the possible voltmeter readings before and after closing switch S? S open A. B. C. D. E. 2V 2V 0V 4V 4V (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) S closed A. B. C. D. E. 4s 8s 12 s 16 s 24 s 42. Energy 4V 2V 4V 0V 2V P X 40. T V+ LDR R1 _ Vout + R3 V- R R2 0V In the above circuit, the output voltage from the operational amplifier is positive. Which of the following changes could cause the output voltage to change to negative? (1) Increasing the value of R1. (2) Decreasing the value of R3. (3) Decreasing the light intensity on the LDR. Q S 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 T) would result in the emission of a photon of wavelength 300 nm? A. B. C. D. E. P Q R S T 98 AL Physics/M.C./P.12 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. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 44. When several neutrons and protons come together to form a stable nucleus, which of the following statements is/are correct? (1) Energy is released. (2) The mass of the nucleus is smaller than the sum of the mass of the individual nucleons. (3) In the nucleus, the electrostatic repulsion between two protons is overcome by the nuclear force between them. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 45. In a nuclear reactor, the 235 92 U nucleus is fissioned by a neutron into two nuclei and a few neutrons are produced. Which of the following statements about this process is/are correct? (1) High energy neutrons are more likely to produce nuclear fission than low energy neutrons. (2) Graphite can be used to absorb excess neutrons. (3) The two nuclei produced have smaller neutron-to-proton ratios than that of the uranium nucleus. A. B. C. D. E. (1) only (3) only (1) and (2) only (2) and (3) only (1), (2) and (3) 98 AL Physics/M.C./P.13 Question No. Key Question No. Key 1. 2. 3. 4. 5. D E D E C 26. 27. 28. 29. 30. B D B A C 6. 7. 8. 9. 10. D E B D D 31. 32. 33. 34. 35. B C B C E 11. 12. 13. 14. 15. A B A D C 36. 37. 38. 39. 40. B D C A D 16. 17. 18. 19. 20. C B A E E 41. 42. 43. 44. 45. C B E E B 21. 22. 23. 24. 25. A A A E C