1 NJC (FOR INTERNAL USE ONLY) 9646/03/2010 [Turn over NATIONAL JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER PHYSICS Paper 3 Longer Structured Questions Candidate answers on the Question Paper. No Additional Materials are required. 9646/03 2 Sep 2010 2 hours Section A For Examiner’s Use 1 2 3 4 READ THE INSTRUCTION FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Answers all questions. You are advised to spend one hour on each section. The number of marks is given in brackets [ ] at the end of each question or part question. Total
Transcript
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NJC (FOR INTERNAL USE ONLY) 9646/03/2010 [Turn over
NATIONAL JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2
CANDIDATE NAME
SUBJECT CLASS
REGISTRATION NUMBER
PHYSICS Paper 3 Longer Structured Questions Candidate answers on the Question Paper. No Additional Materials are required.
9646/03
2 Sep 2010
2 hours
Section A
For Examiner’s Use
1
2
3
4
READ THE INSTRUCTION FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Answers all questions. You are advised to spend one hour on each section. The number of marks is given in brackets [ ] at the end of each question or part question.
Total
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NJC (FOR INTERNAL USE ONLY) 9646/03/2010 [Turn over
Data
speed of light in free space, c = 3.00 x 108 ms-1
permeability of free space, µ0 = 4π x 10-7 Hm-1
permittivity of free space, ε0 = 8.85 x 10-12 Fm-1
elementary charge, e = 1.60 x 10-19 C
the Planck constant, h = 6.63 x 10-34 Js
unified atomic mass constant, u = 1.66 x 10-27 kg
rest mass of electron, me = 9.11 x 10-31 kg
rest mass of proton, mp = 1.67 x 10-27 kg
molar gas constant, R = 8.31 JK-1mol-1
the Avogadro constant, NA = 6.02 x 1023 mol-1
the Boltzmann constant, k = 1.38 x 10-23 JK-1
gravitational constant, G = 6.67 x 10-11 Nm2kg-2
acceleration of free fall, g = 9.81 ms-2
Formulae
uniformly accelerated motion, 2
2
1atuts +=
+=work done on/by a gas, W = p∆V
hydrostatic pressure p = ρgh
gravitational potential, r
Gm−=φ
displacement of particle in s.h.m., x = x0 sin ωt
velocity of particle in s.h.m., tvv ωcos0= and 220 xxv −±= ω
resistors in series, R = R1 + R2 + …
resistors in parallel, ...111
21
++=RRR
electric potential, r
QV
04πε=
alternating current/voltage, x = x0 sin ωt
Transmission coefficient T = ex p(-2kd) Where 2
2 )(8
h
EUmk
−= π
radioactive decay, x = x0 exp (-λt)
decay constant, 2
1
693.0
t=λ
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Section A Answer all the questions in this section.
1 (a) Define the term angular velocity. [1]
(b)(i) A 10 kg baggage is left on a rotating baggage carousel at an airport. The baggage stays at a fixed position on the slope of the carousel and rotates about in a circle (r = 11.0 m) at a constant speed. The frictional force acting on the suitcase is 59.4 N. Use Newton’s Laws to explain why the baggage will experience a net force towards the centre of the circle. [2]
(ii) Show on a fully labelled diagram the forces acting on the baggage. [2]
r
θ = 36.0º
Side View
Direction of rotation
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(iii) Considering the forces acting on the baggage in the vertical direction, show that the normal contact on the baggage is about 78.1 N. [2]
(iv) How much time is required for the suitcase to complete one full rotation? [3]
2 A monoatomic ideal gas is subject to a cycle of changes ABCA . Figure 2 shows a graph of
pressure p against volume V for one cycle of changes for the gas.
Figure 2
(a)(i) Using data from the graph, verify that process BC is isothermal. Show your workings clearly. State an assumption of the gas you must make to support your verification. [2]
p /105 Pa
V /10 - 4 m3
Time taken = ………………..
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(ii) Explain the term internal energy in relation to an ideal gas.
[1]
(b) Temperature of the gas at point C is 385 K. Calculate the temperature of the gas in oC at point A.
[1]
(c)(i) Calculate the change in the internal energy of the gas during the process AB .
[2]
(ii) Work is done by the gas in the change AB . State what must be done to the system for this change to occur. Explain using the first law of thermodynamics.
[2]
Temperature of the gas = ………..………….oC
Change in the internal energy = ……………….. J
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(d) Use the Kinetic Theory of gases to explain why the pressure of an ideal gas increases in the change BC when it contracts at constant temperature.
[2]
3 (a) Describe how an emission line spectrum can be produced in the laboratory. Describe
the appearance of the emission line spectrum when viewed through a grating spectrometer. [3]
(b)(i) The experiment below confirms that electrons occupied only discrete, quantized energy states.
Electrons emitted at the cathode C are accelerated by a potential difference of V1 toward a positively charged grid G, in a glass tube filled with mercury vapor. Beyond the grid is an anode A, held at a voltage of V2 of 1 V negative with respect to the grid.
A graph of anode current Ia against V1 is shown in Figure 3.2.
Figure 3.1 Schematic diagram apparatus
Figure 3.2 Graph of anode current Ia against V1
R
Q
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The values of accelerating voltage where the current dropped gave a measure of the energy necessary to force an electron to an excited state.
Account for the shape of the graph when 1. V1 is less than P. [1]
2. V1 is between P and Q. [1]
(ii) As shown in Figure 3.2, when the accelerating voltage reaches 4.9 V, the current sharply drops, indicating the sharp onset of a new phenomenon. Suggest with explanation what the new phenomenon is. [3]
(iii) 1. Using the values from the graph in Figure 3.2, find the wavelength of the radiation emitted by the mercury atoms as they return to their ground state. [1] 2. State the region of the EM radiation which the wavelength calculated in b(iii)(1) can be found. [1]
Wavelength = ……………….. m
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4 (a) Define the ohm. [2]
(b)(i) The figure below shows a potentiometer setup where the potentiometer wire, ab, is uncalibrated. Es is a known standard cell. Describe how it is used to measure the emf of the unknown source xΕ . [2]
(ii) Discuss one advantage of using the potentiometer setup to measure the emf Ex. [1]
Es
G
E
Ex
switch
a c b
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(c) The potentiometer wire ab of length 1 metre has a resistance of 600 Ω . The rheostat, R, has a resistance 400 Ω for the entire length of 50 cm. The previous circuit has been altered as follows:
(i) Determine the balance length, ac. [2]
(ii) State the direction of the current flowing through the dry cell, Ex, when the rheostat R is
adjusted from the midpoint to the right at the 40 cm mark. [1]
(iii) Find the new balance length, ac’. [2]
G
E = 5.0 V
Ex = 2.0 V
a c b
Rheostat, R = 400 Ω
midpoint 0 cm 50 cm
r = 10 Ω
ac = ……………….. m
ac’ = ……………….. m
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BLANK PAGE
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NATIONAL JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2
CANDIDATE NAME
SUBJECT CLASS
REGISTRATION NUMBER
PHYSICS Paper 3 Longer Structured Questions Candidate answers on the Question Paper. No Additional Materials are required.
9646/03
2 Sep 2010
2 hours
For Examiner’s Use
5
6
7
Section B Answer any two questions. You are advised to spend one hour on each section. The number of marks is given in brackets [ ] at the end of each question or part question. Circle the questions you attempted. Submit Section A and B separately.
Total
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Section B Answer two questions in this section.
5 (a) Ra226
88 is a stationary radioactive isotope which decays to Rn22286 with the release of
an alpha particle. (Mass of He4
2 = 4.00260 u, mass of proton = 1.00783 u,
mass of neutron = 1.00867 u, mass of Rn22286 = 222.018 u)
(i) Define binding energy of a nuclide and explain how this quantity could be a measure of the stability of a nuclide. [2]
(ii) Given the binding energy per nucleon of Ra22688 is 7.66831 MeV, show that its mass is
226.025 u. [2]
(iii) Starting from first principles, show that
Q = Kα ( )1RnM
Mα+
where Q is the energy released in the decay reaction, Kα is the kinetic energy of the alpha particle, Mα is the mass of the alpha particle and MRn is the mass of Rn222
86 . [3]
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(iv) Hence, calculate Kα. [3]
(v) Radon (Rn) decays by alpha emission to polonium and a tube containing an isotope of radon is to be implanted in a patient. Suggest and explain two reasons why an alpha emitter is preferred to the beta or gamma emitter for such purpose. [2]
(b) The graphs below show the activity of two samples of sodium nuclides, X and Y.
X
Y
Kα = ……………….. J
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(i) Define activity and half-life of a radioactive nuclide. [2]
(ii) Determine the ratio
nuclei undecayed
nuclei undecayed
Yofnumber
Xofnumber when the activities of the two
samples are the same. [2]
(iii) How would you tell from the graphs, as drawn, that the background radiation is negligible? [2]
(iv) Explain clearly how you would show that the activity of the nuclides decay exponentially. [2]
Ratio =………………..
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6 (a) State what is meant by coherent waves. [1]
(b)(i) Two coherent sources of sound waves are located at position X and Y as shown in
Figure 6.1 below. The sources have zero phase difference. An observer stands at position O. If the frequency of the sound wave is 660 Hz, with suitable calculations, determine whether or not the observer experiences constructive or destructive interference. (Take the speed of sound to be 330 ms-1) [3]
Figure 6.1
(b)(ii) The source at position Y is slowly moved to the right until it eventually reaches position Y’, as shown in Figure 6.2. Describe what is experienced by the observer at O while the source is being moved. [2]
Figur e 6.2
Sound source at X
9 m
12 m
Sound source at Y’
9 m
Observer at O
Sound source at X
9 m
12 m
Observer at O
Sound source at Y
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(b) (iii)
Would you expect the observer to hear complete silence when there is destructive interference? Explain. [1]
(c) The setup in (b)(i) has been changed by replacing one of the sound sources with a reflecting plane (as shown in Fig 6.3). With suitable calculations, describe what is experienced by observer at O. (Note that reflected wave from a hard surface undergoes a phase change of π radian with respect to the incident wave. [3]
Fig 6.3
(d) Explain what is meant by diffraction of a wave. [2]
8 m
12 m
Observer at O
Reflecting plane
Sound source at Y
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(e) A simplified model of the way the human eye responds to light of different wavelengths incident normally on a diffraction grating of spacing d = 2.5 µm is as follows: Light: Perceived as: Single wavelength between 0.40 µm and 0.50 µm Blue Single wavelength between 0.50 µm and 0.60 µm Green Single wavelength between 0.60 µm and 0.70 µm Red
Determine whether there is any overlapping between the first order and second order spectra. [3]
(f) The spectrometer setup below shows how light from a collimator is made to fall normally on a diffraction grating.
The telescope can be used to locate the second order bright fringes of any particular wavelength, λ at angular positions 1θ and 2θ . Sodium vapour lamp of wavelength
589.3 nm is first used and the angle between 2θ and 1θ , θ is shown in the table below. The sodium vapour light is then replaced by a discharge tube containing a mixture of gases and the θ values are recorded in table below for two pairs of second order bright fringes.
NJC (FOR INTERNAL USE ONLY) 9646/03/2010 [Turn over
7 (a)(i) Define power. [1]
(ii) Derive an equation for power in terms of force and velocity. [2]
(b) Solar Impluse (see figure below), a plane powered by sunlight, ended its flight in Switzerland on 8 Jul 2010 after remaining aloft for 26 hours. It was able to fly in the darkness powered entirely by the energy its batteries had stored during the daytime flight.
(i) Describe qualitatively the energy transformation that takes place during the flight. [3]
Solar cells
Electric Engine
Solar Impulse
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(ii) During the day, the average intensity of the sunlight received by the plane was 250 Wm-2. The solar panel covers an area of 200 m2. The average power achieved by the plane’s four engines is 6.0 kW.
1. Show that the efficiency of the solar cells and its battery system is about 12%. [2]
2. The average flying speed of the aircraft is 70 kmh-1. Determine the magnitude of the air resistance acting on the aircraft. [2]
3. For a daylight period of 14 hours, calculate the solar energy needed to be stored in the battery so as to complete the entire flight. [2]
(c) The aircraft is powered by 12,000 solar cells. Solar cells use p-n junctions to convert sunlight directly into electricity. With the aid of a diagram, discuss qualitatively the origin of the depletion region in a p-n junction. [4]
Air resistance = ……………..….. N
Energy required = ……………..… J
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(d)(i) To provide a useful supply for the plane, a bank of solar cells consists of many cells connected in a series and parallel array. The figure below shows the arrangement, using a smaller number of cells than is used in practice. Give one advantage for connecting the cells 1. in series as shown in selection A. [1] 2. in parallel as shown in selection B. [1]
(ii) Even if the arrangement of supplies as shown above are installed and in working order, there may be still no power available. Explain why this could happen and what might be done to provide suitable back-up power. [2]
