stpm trial 2012 physics qa kelantan

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    SECTION A; Answer all the questions

    1. For an object moving with uniform acceleration, the velocity v is given by the equation v2

    = p +qx, where p and q are constants and x is a variable.What are the dimensions of the term qx?

    A L B LT-1 C LT-2 D L2T

    -2

    2. A ball is thrown vertically upwards. The upward direction is considered the positive direction.Assuming that air resistance is negligible, which of the following statements is correct?A When the ball is at the highest point, its acceleration is zeroB Its velocity is negative during the upward and downward motions.C Its acceleration is negative during the upward and downward motions.D Its displacement from the point of projection is negative during the upward and downwardmotions

    3. A car of mass 1250 kg accelerates from 0 to 100 km h-1

    A 121 kW

    in 4.0 s. The average power of the caris

    B 341 kWC 484 kWD 681 kW

    4. A particle moves with constant speed in a horizontal circle. Which of the following quantities iszero?

    A Angular velocityB Angular accelerationC Centripetal accelerationD Resultant force

    5. A bicycle wheel of radius 0.2 m can rotate freely about a fixed axis. A constant force of 3 N isapplied tangentially to the wheel for 0.4 s. The wheel starts to rotate from rest and its moment ofinertia about the axis of rotation is 0.5 kg m2

    . What is its angular velocity after 0.4 s?

    A 0.12 rad s-1

    B 0.48 rad s

    -1

    C 0.20 rad s

    D 0.60 rad s

    -1-1

    6. The figure shows a rod pivoted at point P on a smooth horizontal surface.

    Two forces, each of magnitude 5.0 N acting in opposite directions, are applied at the two ends ofthe rod. The resultant torque on the rod is

    A 2.5 N m B 12.5 N m C 21.7 N m D 25.0 N m

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    13. The velocity-time (v-t) graph for a car is as shown in the graph..

    Which of the following is the displacement-time (s-t) graph for the car?

    14. Which one of the following is not a valid example of action and reaction to which Newton'sThird Law of Motion applies?

    A The forces of attraction between an electron and a proton in a hydrogen atomB The forces of repulsion between two parallel wires carrying currents in opposite directions.C The forces of attraction between two gas molecules passing near each otherD The weight of a satellite and the centripetal force keeping the satellite in orbit

    15. When a force of 8 N acts on an object of mass 4 kg for 2 s, what is the rate of change ofmomentum of the object?

    A 2 kgms-2 B 4 kgms-2 C 8 kgms-2 D 16 kg ms

    -2

    16 A transverse periodic wave described by the expression (where y and x are inmeters and t is in seconds) is established on a string. Which one of the followingstatements concerning this wave is false?

    A The wave is traveling in the negative x direction.B The amplitude is 1.0 m

    C The wavelength of this wave is 2.0 m.D The wave travels with speed 5.0 m/s.

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    17 A loudspeaker at the base of a cliff emits a pure tone of frequency 3000.0 Hz. A manjumps from rest from the top of the cliff and safely falls into a net below. How far hasthe man fallen at the instant he hears the frequency of the tone as 3218.0 Hz? Thespeed of sound is 343 m/s.

    A 12.2 m B 15.3 C 31.7 D 46.8

    18The physical process not observable for sound waves is

    A ReflectionB RefractionC InterferenceD Polarization

    19 The graph shows the potential energy curves of two kinds of solid P and Q.

    Which among the following statements is nottrue of P and Q

    A Solid P has a higher specific latent heat than that of solid QB Solid P has a higher force constant than that of solid QC The molecular bond in solid P is stronger than or solid QD The molecules of solid P reaches the minimum potential energy at a temperature

    lower than that of solid Q

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    20 The diagram below shows a light rod, of length a , hung from the lower ends of thewires P and Q so that both the wires are vertical. P and Q possess the same natural

    length and the same natural radius but each possess different Young modulus of1

    E

    and2

    E respectively. A load is placed on the rod at a distance x from wire P so that

    the rod will remain horizontal

    P Q

    load

    RodX

    a

    What is the value of x in terms of a , 1E and 2E

    A2

    1

    E

    aE B

    21

    1

    EE

    aE

    + C

    21

    2

    EE

    aE

    + D

    ( )

    1

    21

    E

    aEE +

    21

    Figure 14.9 shows two isothermals for an ideal gas of fixed mass at temperatures

    1T and

    2T . The ratio

    2

    1

    T

    T is

    A4

    1 B

    2

    1 C 1 D 4

    22 Which of the following shows correctly the relation between the mean speed v , the

    ms speedrms

    v , and the most probable speedov of the molecules of a gas?

    A v rms

    v

    Brms

    v ov

    Cov v

    Drms

    v ov

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    23 According to the kinetic theory of gases, the internal energy of an ideal gas is bestdefined as

    A The average kinetic energy of the molecules of gas.B The total kinetic energy of the molecules of gasC The mast probable kinetic energy of the gas moleculesD The total potential energy and the kinetic energy of the molecules of the gas

    24 An ideal monoatomic gas with an initial volume of V at the initial pressure of p

    expands adiabatically to a pressure of32

    p. The new volume of gas is

    A 4 V B 8 V C 8 V D 32 V

    25 Which one of the following statements provides the most convincing evidence thatvisible light is

    a form of electromagnetic radiation?

    A Two light sources can be coherent.B Light can be reflected from a surface.C Light can be diffracted through an aperture.D Light can form a double-slit interference pattern.

    26 A charge q = 4.0 C is moved 0.25 m horizontally to point P in a region where anelectric field is 150 V/m and directed vertically as shown. What is the change in theelectric potential energy of the charge?

    A -2.4 x 10B

    -3

    -1.5 x 10C

    -4+1.5 x 10

    D

    -4

    Zero Joules

    27 The figure below shows four parallel plate capacitors: A, B, C, and D. Each

    capacitor carries the same charge q and has the same plate areaA. As suggestedby the figure, the plates of capacitorsA and C are separated by a distance d whilethose of B and D are separated by a distance 2d.Capacitors A and B are maintained in vacuum while capacitors C and D containdielectrics with constant = 5.

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    A A B C D C BADCB A B D C D BACD

    28 If the work required to move a +0.35 C charge from pointA to point B is +125 J,

    what is the potential difference between the two points?A ZeroB 44 VC 88 VD 360 V

    29 In the circuit below, switch S is connected to position 1 at time t = 0. At the instantt =T, when the voltmeter reading reaches Vo, the switch S is connected to theposition 2.

    Which of the following graphs shows the variation of the voltmeter reading V withtime t?

    A

    A B

    C D

    30 Which one of the following statements is true concerning the spacing of the electricfield lines in thevicinity of two point charges of equal magnitude and opposite sign?

    A It indicates the direction of the electric field.B It does not depend on the magnitude of the charges.C It is large when the magnitude of the charges is large.D It indicates the relative magnitude of the electric field.

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    31 Which one of the following statements concerning the magnetic force on a chargedparticle in amagnetic field is true?

    A It is zero if the particle moves perpendicular to the field.B It is a maximum if the particle moves parallel to the field.C It acts in the direction of motion for a positively charged particle.D It depends on the component of the particle's velocity that is perpendicular to the

    field.

    32 Two electrons are located in a region of space where the magnetic field is zero.ElectronA is atrest; and electron B is moving westward with a constant velocity. A non-zeromagnetic fielddirected eastward is then applied to the region. In what direction, if any, will eachelectron be

    moving after the field is applied?

    A Upward away from earth westwardB at rest westwardC northward eastwardD at rest eastward

    33 A proton is traveling south as it enters a region that contains a magnetic field. Theproton isdeflected downward toward the earth. What is the direction of the magnetic field?

    A downward B west C north D

    east

    34 A long, straight wire carries a current I. If the magnetic field at a distance d from thewire hasmagnitude B, what is the magnitude of the magnetic field at a distance 2d from thewire?

    A B/2 B 2B C B/4 D 4B

    35 The current in a certain ac circuit is independent of the frequency at a given voltage.

    Whichcombination of elements is most likely to comprise the circuit?

    A F/sB F sC D W b

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    36 A battery is used to drive a circuit. After a certain amount of time, the current is zeroamperes. Whenthe same circuit is driven by an ac generator, the current is non-zero and alternates.Whichcombination of elements is most likely to comprise the circuit?

    A resistors only

    B inductors onlyC capacitors onlyD a combination of inductors and resistors

    37 A variable inductor is connected to an ac source. What effect does increasing theinductance have onthe reactance and current in this circuit?

    Reactance Curren tA no change no changeB decreases no changeC decreases increasesD increases decreases

    38 When the frequency of an ac circuit is increased at constant voltage, the currentincreases and thendecreases. Which combination of elements is most likely to comprise this circuit?

    A resistors onlyB capacitors onlyC a combination of inductors and resistorsD a combination of inductors and capacitors

    39 Which one of the following types of wave is intrinsically different from the other four?(a) (c) (e) visible light(b) (d)

    A radio wavesB sound wavesC gamma raysD ultraviolet radiation

    40 What is the correct order, beginning with shortest wavelength and extending to thelongest

    wavelength, of the following colors in the visible light spectrum: blue, green, red,violet, andyellow?

    A red, yellow, blue, green, violetB violet, blue, yellow, red, greenC red, yellow, green, blue, violetD violet, blue, green, yellow, red

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    41 Which one of the following statements concerning the energy carried by anelectromagnetic waveis true?

    A The energy is carried only by the electric field.B More energy is carried by the electric field than by the magnetic field.

    C The energy is carried equally by the electric and magnetic fields.D More energy is carried by the magnetic field than by the electric field.

    42 The most convincing evidence that electromagnetic waves are transverse waves isthat

    A they can be polarized.B they carry energy through space.C they can travel through a material substance.D they do not require a physical medium for propagation.

    43 Linearly polarized light is incident of a sheet of polarizing material. The anglebetween thetransmission axis and the incident electric field is 52. What percentage of theincident intensityis transmitted?

    A 38 % B 43 % C 52 % D 62 %

    44 Which one of the following statements provides the most convincing evidence thatvisible light is a form of electromagnetic radiation?

    A Two light sources can be coherent.B Light can be reflected from a surface.C Light can be diffracted through an aperture.D Light can form a double-slit interference pattern.

    45 Which one of the following quantities is not necessarily conserved in nuclearreactions?

    A electric chargeB number of protons

    C linear momentumD angular momentum

    46 The nucleus of a certain isotope of tin contains 68 neutrons and 50 protons. Whichsymbolcorrectly represents this isotope?

    A Sn68

    50

    B Sn50

    68

    C Sn118

    50

    D Sn118

    68

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    47 Which model of atomic structure was developed to explain the results of the

    experiment shown?

    A Bohr modelB nuclear atomC billiard ball atomD plum-pudding model

    48 Which one of the following pairs of characteristics of light is best explained byassuming thatlight can be described in terms of photons?

    A photoelectric effect and the effect observed in Young's experimentB diffraction and the formation of atomic spectraC polarization and the photoelectric effectD existence of line spectra and the photoelectric effect

    49 Determine the wavelength of incident electromagnetic radiation required to cause anelectron transition from the n = 6 to the n = 8 level in a hydrogen atom.

    A 1.2 x103

    Bnm

    2.2x103

    Cnm

    3.4 x 103

    Dnm

    7.5 x103

    nm

    50 Which one of the following statements concerning the cutoff wavelength typicallyexhibited in X-ray spectra is true?

    A The cutoff wavelength depends on the target material.B The cutoff wavelength depends on the potential difference across the X-ray tube.C The cutoff wavelength is independent of the energy of the incident electrons.D The cutoff wavelength occurs because of the mutual shielding effects of K-shell

    electrons

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    OBJECTIVE ANSWER SCHEME

    N0 Answer No Answer

    1 D 26 D

    2 C 27 C3 A 28 D

    4 A 29 C

    5 B 30 D

    6 B 31 D

    7 B 32 B

    8 A 33 B

    9 D 34 A

    10 B 35 C

    11 C 36 C12 D 37 D

    13 D 38 D

    14 B 39 B

    15 D 40 D

    16 D 41 C

    17 C 42 A

    18 D 43 A

    19 D 44 D

    20 C 45 B21 D 46 D

    22 B 47 B

    23 D 48 D

    24 C 49 D

    25 D 50 B

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    STPM 2012 - 1 -

    960/2*This question paper is CONFIDENTIAL until the examination is over CONFIDENTIAL*

    SECTION A: Answer all questions

    1. State Newtons third law of motion. [1]

    (a) A brick is lying on the ground as shown in figure 1, with the forces shown actingon it. Write down what these forces are and with them their corresponding reactionpair. [3]

    R

    fig.1 W

    (b) What are the characteristic of this force? [2]

    3. (a) Define intensity level, . [2]

    (b) A recording engineer works in a soundproofed room that is 44.0 dB quieterthan the outside. If the sound intensity in the room is 1.2 X 10-10 W m-2

    , what is theintensity outside? [4]

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    STPM 2012 - 2 -

    960/2*This question paper is CONFIDENTIAL until the examination is over CONFIDENTIAL*

    4. A jet plane is made of different classes of materials with different properties.The table below indicates a certain material with its properties. Explain why suchmaterial is suitable for certain part of the jet plane. Sketch on the given axis to

    Material Properties

    Part of the

    Jet-plane Graph Stress vs Strain

    DurulaminExteriorbody of the

    jet plane

    Stress

    strain

    Ceramicrotor blade in

    jet engines

    Stress

    strain

    RubberTyre

    Stress

    strain

    [6]

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    STPM 2012 - 3 -

    960/2*This question paper is CONFIDENTIAL until the examination is over CONFIDENTIAL*

    5. Two long, straight wires separated by0.10 m carry currents of 18 A and 6 A in thesame direction as shown in the figure

    (a) Determine the magnitude of the magnetic field at the point P. [4]

    (b) What is the direction of the magnetic field at the point P? [1]

    6. Draw a circuit diagram for either inverting amplifier ornon-inverting amplifier.Explain your circuit. [6]

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    STPM 2012 - 4 -

    960/2*This question paper is CONFIDENTIAL until the examination is over CONFIDENTIAL*

    7. A physics professor wants to find the diameter of a human hair by placing itbetween two flat glass plates, illuminating the plates with light of vacuum wavelength

    = 552 nm and counting the number of bright fringes produced along the plates. The

    prof finds 125 bright fringes between the edge of the plates and the hair. What is thediameter of the hair? [4]

    8. An electron with a kinetic energy of 1.2 x 10-18

    J collides with an electron in orbitaround an atom, causing it to jump from 6.2 eV level to 1.5 eV level. What is thefinal KE of the first electron? [4]

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    STPM 2012 - 5 -

    960/2*This question paper is CONFIDENTIAL until the examination is over CONFIDENTIAL*

    Section B: Answer any four question

    9. (a) Define impulse. What are the units for impulse? [2](b) A spaceship of mass 4000 kg is moving with a constant velocity of 3.12 x 10

    5ms

    -1.

    It is suddenly hit by a mysterious impulse of 1.65 x 105

    Ns in the opposite direction to

    its motion. What is its final velocity and direction of motion? [4]

    c) (i) Explain why parachutists bend their knees and roll when they hit the ground.[2](ii) If the parachutists mass is 80 kg, and the velocity of the impact is 12 m s

    -1

    , whatis the minimum time required for the impact if the parachutist does not break a leg?Take the force required to break a leg is 600 N. [7]

    10.(a) i. Name one physical example of a longitudinal wave motion. [1]

    ii. What features do longitudinal wave have in common with transverse wave? [3]

    (b) Explain, using clearly labeled sketches where appropriate, the meaning of the followingterms when applied to wave motion.i. displacementii. amplitudeiii. wavelengthiv. phase difference between two waves [4]

    (c) The excess pressure in a traveling sound wave is given by the equation

    p = 1.5 sin ( )

    tx 330

    2

    where x and in metres, t in seconds & p in Pa

    (i) What is the velocity of the wave?(ii) If = 2 m, what is the frequency of the wave?(iii) What is the maximum pressure ( pressure amplitude)?

    (iv) What is the pressure at x =6

    1and t = 0? [7]

    11. The first law of thermodynamic, an application of energy conservation, statesthat the change in internal energy, U, of a system is equal to the sum of the changesof heat energy Q and work done W by or on the system.(a) Use this law to explain water boiling and heating a gas at constant pressure.

    [6](b) What is the relation between the specific heats, at constant pressure andconstant volume? [4]

    (c) What is a field? Sketch the variation of g inside and outside the Earth andvariation of E and VE

    inside and outside a hollow conductor. Explain. [5]

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    STPM 2012 - 6 -

    960/2*This question paper is CONFIDENTIAL until the examination is over CONFIDENTIAL*

    12. ( a) What is the relation between resistance and resistivity?Compute the resistance of 180 m of silver wire ( 1.6 x 10

    -8) having a cross section of

    0.3 mm2

    . [3]

    (b) If a battery or other source of emf has internal resistane, then the terminal voltage

    does not equal to the emf when current is flowing. What are the relations between emfand terminal voltage in such situations? [4]

    (c) A 1400 resistor is connected in series with a 200 resistor and a 12 V battery.i. How much does the current in the circuit change when a 5000 voltmeter is

    connected across ( in parallel with) with the 1400 resistor?ii. Across the 200 resistor?iii. What does the voltmeter read in (i)?iv. In (ii)? [8]

    13. (a) Define the following properties of lenses: converging, diverging, focal length,

    power and diopter. [5](b) A convexo-concave lens has faces of radii 3 and 4 cm, respectively, and is madeof glass of refractive index 1.6. Determine its focal length and the linear magnificationof the image when the object is 28 cm from the lens. [5](c) A grating have 15 000 lines per cm produces spectra of a mercury arc. The greenline of the mercury spectrum has a wavelength 5461. What is the angularseparation between the first order green line and second order green line. [5]

    14 (a) StateBohrs postulate for an atom. [2]

    (b) Statefour most important results from a photoelectric effect experiment.. [4]

    (c) State two laws of conservation in radioactive decay. [2]

    (d) Explainhow X-ray is diffracted at high intensity in certain directions by

    a crystal. [3]

    (e) Explainthe working principle of a mass spectrometer to measure the massesof ions. [4]

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    OBJECTIVE ANSWER SCHEME

    N0 Answer No Answer

    1 D 26 D

    2 C 27 C

    3 A 28 D

    4 A 29 C

    5 B 30 D

    6 B 31 D

    7 B 32 B

    8 A 33 B

    9 D 34 A

    10 B 35 C

    11 C 36 C12 D 37 D

    13 D 38 D

    14 B 39 B

    15 D 40 D

    16 D 41 C

    17 C 42 A

    18 D 43 A

    19 D 44 D

    20 C 45 B21 D 46 D

    22 B 47 B

    23 D 48 D

    24 C 49 D

    25 D 50 B

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    schemeSECTION A: Answer all questions

    1. State Newtons third law of motion. [1]

    Every force that acts on an object has an equal and opposite force reacting to it.

    (a) A brick is lying on the ground as shown in figure 1, with the forces shown acting onit. Write down what these forces are and with them their corresponding reaction pair.[3]

    W = gravitational pull of the Earth on the brick RIts reaction force is the gravitational pull of the brickon the Earth. ..........................................................1

    R = normal contact force of the ground on the brickits reaction force is the normal contact force of the brick Won the ground .........................................................1

    (b) What are the characteristic of the forces? [2]

    All the forces occur in action-reaction pair must be equal in magnitude & opposite in direction ................................1 the same type of force & acting on different objects ..................1

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    3. (a) Define intensity level, . [2]

    Intensity level,is defined as = 10 log10

    0I

    I dB, ..........................1

    Where0

    I = 10-12W m-2

    lowest intensity at a given frequency that can be heard 0 dB) ........1

    ( known as threshold hearing which is the

    The decibel, dB is a measurement unit used when comparing two soundintensities. It is dimensionless (like radian)

    (b) A recording engineer works in a soundproofed room that is 44.0 dB quieter thanthe outside. If the sound intensity in the room is 1.2 X 10-10 W m-2

    , what is the intensityoutside?

    outside=inside

    = (10 dB) log

    + 44.0 dB

    0.44

    0

    +

    I

    Iinside ....................................................1

    = (10 dB) log 0.44101

    102.1

    12

    10

    +

    = 20.8 + 44.0 = 64.8 dB .......1

    The sound intensity outside the room is,

    utsideI

    0=

    0I 10 dB

    outside

    10

    = ( ) 108.64

    12101000.1

    ......................................1

    = 3.02 x 10-6W m-2

    ...................................1

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    4. A jet plane is made of different classes of materials with different properties.The table below indicates a certain material with its properties. Explain why suchmaterial is suitable for certain part of the jet plane. Sketch on the given axis to

    Material Properties

    Part of the

    Jet-plane Graph Stress vs Strain

    Durulamin

    Tough & stiffshow plasticdeformation beforebreaking

    Exteriorbody of the

    jet plane

    Stress

    strain

    Ceramic

    Brittle but very strong.It has the ability toresist hightemperature rotor blade in

    jet engines

    Stress

    strain

    Rubber

    Highly elasticbehaviour extendseasily until it reachesa point where itbecomes hard tostretch again

    Tyre

    Stress

    strain

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    5. Two long, straight wires separated by0.10 m carry currents of 18 A and 6 A in thesame direction as shown in the figure

    (a) Determine the magnitude of the magnetic field at the point P. [4]B = 4.8 10-5

    T

    (b) What is the direction of the magnetic field at the point P? [1]

    Into the plane of the page

    6. Draw a circuit diagram for either inverting amplifier ornon-inverting amplifier.Explain your circuit. [6]

    Inverting Amplifier Non-inverting Amplifier

    1. Circuit diagram

    *The +input is grounded VQ*The input is connected to V

    = 0

    insignal via R

    * The path through Rf

    f

    *The amplifier function in a close-loop mode

    acts as a path for

    feedback negative

    1. Circuit diagram

    *The Vin

    is connected to the + input

    *The path through Rf

    *The amplifier function in a close-loop mode

    acts as a path for

    feedback negative

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    7. A physics professor wants to find the diameter of a human hair by placing itbetween two flat glass plates, illuminating the plates with light of vacuum wavelength

    = 552 nm and counting the number of bright fringes produced along the plates. Theprof finds 125 bright fringes between the edge of the plates and the hair. What is thediameter of the hair?

    The reflection from the boundaries will cause a net 1800

    The condition for bright fringe is 2t = ( m + ) phase shift.

    film

    and m = 124, since there is bright fringe for m = 0. and

    ............................................1

    filmn

    =

    t =2

    2

    1filmm

    +

    =n

    m

    2

    2

    1

    +

    ....................................................................1

    =

    00.12

    105522

    1124

    9

    +

    .......................................................1

    = 3.44 x 10-5

    m ................................................................1

    8. An electron with a kinetic energy of 1.2 x 10-18

    J collides with an electron in orbitaround an atom, causing it to jump from 6.2 eV level to 1.5 eV level. What is thefinal KE of the first electron? [4]

    Change in energy, E2 E1 = 4.7 eV

    = 1.5 (6.2) .................................................1

    = 4.7 x 1.6 x 10

    = 7.52 x 10

    -19

    -19

    J ................................................1

    The final Kinetic Energy = 1.2 x 10-18 7.52 x 10-19 ...............................1= 4.48 x 10-19

    J ................................................1

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    Section B: Answer any four question

    9. (a) Define impulse. What are the units for impulse? [2]

    Impulse is change in momentum. ..........................................................1

    unit: Ns or kg m s

    -1

    .....................................................................1

    (b) A spaceship of mass 4000 kg is moving with a constant velocity of 3.12 x105ms-1. It is suddenly hit by a mysterious impulse of 1.65 x 105

    [4]

    Ns in the oppositedirection to its motion. What is its final velocity and direction of motion?

    Impulse, I = m (v u ) ......................................................................11.65 x 105 = 4000 ( v 3.12 x 105

    v = 1.01 x 10) .................................................1

    5m s-1

    .......................................................1

    It moves backwards .......................................................................1

    (c) (i) Explain why parachutists bend their knees and roll when they hit the ground.It is to spread out the time of the impact, and so reduce the force actingon the parachutist. ............................................................................2

    (ii) If the parachutists mass is 80 kg, and the velocity of the impact is 12 m s-1

    ,what is the minimum time required for the impact if the parachutist does not break aleg? Take the force required to break a leg is 600 N.

    Weight of parachutist = 80 x 9.81 = 784.8 N ......................................1

    Maximum force that can be produced by the leg before breakingL = 2 x 600 = 1200 N .....................................1Left over force for decelerating acting in opposite direction to the motion

    F = W L ...............................................................1= 784.8 1200 ...................................................1= 415.2 N .......................................................1

    Impulse, Ft = m (v u )

    t =( ) ( )( )

    2.415

    12800

    =

    F

    mumv1

    t = 2.31s .............................................................1

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    10.(a) i. Name one physical example of a longitudinal wave motion. [1]

    - sound wave .............................................................................................................1

    ii. What features do longitudinal wave have in common with transverse wave?[3]

    -They both transmit energy from the source

    -Repeats its pattern at equal distance, i.e. have a definite wavelength-Profile of wave repeats equal number of times per second, i.e. have a definite frequency

    -Travel at the speed given by fv= where wavelength

    -Have a definite amplitude but can form standing waves.

    -They both transmit energy from the source

    any three points ..........................................................................3

    (c) The excess pressure in a traveling sound wave is given by the equation

    p = 1.5 sin ( )

    tx 330

    2

    where x and in metres, t in seconds & p in Pa

    (i) What is the velocity of the wave?

    p = - 1.5 sin

    330

    3302

    xt

    equivalent y = y0

    v

    xtv2sin 1

    v = 330 m s-1

    (ii) If = 2 m, what is the frequency of the wave?.1

    v = f ......................................................................................................................1330 = f (2)

    f = 165 Hz ............................................................................................1

    (iii) What is the maximum pressure ( pressure amplitude)?

    p0

    = 1.5 Pa ......................................................................................................1

    (iv) What is the pressure at x =6

    1and t = 0?

    p = - 1.5sin 75.0

    6

    sin5.1

    330

    6

    1

    0

    2

    3302 ==

    Pa .....................................2

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    11. The first law of thermodynamic, an application of energy conservation, states thatthe change in internal energy, U, of a system is equal to the sum of the changes ofheat energy Q and work done W by or on the system.(a) Use this law to explain water boiling and heating a gas at constant pressure. [6]

    First Law of thermodynamics: U =Q +WBoiling water:Q is positive as heat is going into the system ....................................................1

    W is negative as water expands when it changes state ....................................1U is positive the system is changing state so potential energy increases ......1

    heating a gas at a constant volumeQ is positive as heat is going into the system .....................................................1

    W is zero because the volume is fixed ...............................................................1

    U is positive as the temperature is increasing ....................................................1

    (b) What is the relation between the specific heats, at constant pressure and constantvolume? [4]

    When gas is heated at constant volume, the entire heat energy supplied goes to

    increase the internal energy of the gas molecules. ..................................................But

    when a gas is heated at constant pressure, the heat supplied not only increases the

    internal energy of the molecules but also does the mechanical work in expanding the

    gas against the opposing constant pressure. .......................................................1Hence the specific heat of gas at constant pressure, cpis greater than it specific heat at

    constant volume, cv

    It can be shown that for an ideal gas of molecular weight M,

    . ........................................................................................1

    cp cv = R/M where R is universal gas constant. ...........................1

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    11 (c) What is a field? Sketch the variation of g inside and outside the Earth andvariation of E and VE

    inside and outside a hollow conductor. Explain.

    A field is a region of space where force can be felt ........................................1

    V uniform acrossconductor

    V V 1/r ..1

    g rg increase g decreases E r

    uniformly g2

    1

    r ..1

    1

    r

    12. ( a) What is the relation between resistance and resistivity?Compute the resistance of 180 m of silver (( 1.6 x 10-8)wire having a cross section of0.3 mm2

    R =

    . [3]

    A

    L whereis resistivity .................1

    R =A

    L= ( 1.6 x 10-8

    10103.0

    180

    ) = 9.6 .......................................................2

    (b) If a battery or other source of emf has internal resistance, then the terminal voltagedoes not equal to the emf when current is flowing. What are the relations between emfand terminal voltage in such situations? [4]

    The terminal voltage of a battery or generator when it delivers a current I is equal to thetotal emf minus the potential drop in its internal resistance,r. ..................................... 1- When delivering current ( on discharge), terminal voltage = emf Ir .......................1-When receiving current ( on charge ) terminal voltage = emf + Ir .......................1- When no current exist, terminal voltage = emf of the battery .....................................1

    Earth Hollowconductor(charged)

    E decreases as it hadstarted decreasing from thecenter, E 1/r2 ..........1

    E equals potentialgradient which is zero

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    (c) A 1400 resistor is connected in series with a 200 resistor and a 12 V battery.

    i. How much does the current in the circuit change when a 5000 voltmeter isconnected across ( in parallel with) with the 1400 resistor? [8]

    Original I =2001400

    12

    += 7.50 mA .................................................................1

    Placing 5000 parallel with 1400 , R-11400

    1

    5000

    1+= , R = 1093 ...........1

    mAI

    mAI

    78.150.728.9

    28.92001093

    12

    ==

    =+

    = .....................................2

    ii. Across the 200 resistor?

    Placing 5000 parallel with 200 , R-1200

    1

    5000

    1+= , R = 192.3

    mAmAmAI

    mAI

    036.050.7536.7

    54.714003.192

    12

    ==

    =+

    = ..............2

    iii. What does the voltmeter read in (i)?

    The drop across 1400 is, V = 12 200 ( 9.28 x 10-3

    (without voltmeter, potential drop = 10.5 V)

    ) = 10.15 V ..................1

    iv. In (ii)?

    Voltmeter reads: 12 (1400) x (7.536 x 10-3

    ( instead of 1.5 V without the voltmeter )) = 1.45 V ...................................1

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    13. (a) Define the following properties of lenses: converging, diverging, focal length,power and diopter. [5]

    Converging lens is one that focuses parallel ray to a point .......................................1

    A diverging lens is one that spreads parallel ray ........................................................1

    Focal length refers to the distance from the lens to either principal focus. ................1

    Power of a lens is the reciprocal of the focal length in metres. ...................................1

    A diopter is the unit for the power of a lens, equal to the power of a lens of focal length

    one metre ..................................................................................................................1

    (b) A convexo-concave lens has faces of radii 3 and 4 cm, respectively, and is made ofglass of refractive index 1.6. Determine its focal length and the linear magnification of

    the image when the object is 28 cm from the lens. [5]

    ( ) ( ) 5.012

    16.0

    4

    1

    3

    116.1

    2

    111

    1

    1

    =

    =

    =

    =RR

    nf

    cmf 20= .......................2

    uvf

    111+= =

    v

    1

    28

    1

    20

    1+= v = 70 cm ..............................................................2

    linear magnification = 5.228

    70==

    u

    v .....................................................................1

    (c) A grating have 15 000 lines per cm produces spectra of a mercury arc. The greenline of the mercury spectrum has a wavelength 5461. What is the angular separationbetween the first order green line and second order green line.

    n = 1

    sindn = 8192.0

    100150001

    1054611sin

    10

    1 =

    ==

    d

    n

    14 (a) StateBohrs postulate for an atom. [2]

    The electron in an atom moves in a circular orbit about the nucleus...1

    Only certain permissible/stable/quantised / stationary states circular orbit areallowed. ..1

    Energy emitted only when electron transits from higher to lowerorbit....1

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    any 2 marks

    (b) Statefour most important results from a photoelectric effect experiment..

    - When the intensity of the light is increased, the magnitude of the current

    increases. ........................................................................................................1 When the frequency of the light increases, the stopping potential remain constant.

    ...1 There exist a cut-off threshold frequency (below which no electron is ejected no

    matter how intense the light). ...1 The ejection of photoelectrons is immediate. ....1 When the frequency of light is increased the stopping potential increases / the

    maximum KE of electron increases. ...1any four marks

    (c) State two laws of conservation in radioactive decay. [2]

    conservation of charge (or proton number) ......................................................1conservation of mass number (or nucleon number) ..........................................1conservation of mass-energy or ......................................................................1conservation of momentum ............................................................................1

    any 2

    (d) Explainhow X-ray is diffracted at high intensity in certain directions bya crystal. [3]

    Atoms as secondary source / X-ray is diffracted by atoms ..1Path difference = n .1Constructive interference happen / in phase happen 1

    (e) Explainthe working principle of a mass spectrometer to measure the masses of

    ions. [4]

    - Ions are accelerated through an electric field and its velocity determined......1

    - Ions are then deflected in a magnetic field. .....1- The magnetic field / electric field are adjusted until the ions are detected.

    ..1- The mass is calculated from the magnitude of the electric field and magnetic field.

    ....1