Stpm Trial 2009 Phy Q&a (melaka)

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STPM TRIAL 2009

PERSIDANGAN KEBANGSAAN PENGETUA-PENGETUA SEKOLAH MENENGAH MALAYSIA CAWANGAN MELAKA PENILAIAN PENGESANAN PEPERIKSAAN SIJIL TINGGI PERSEKOLAHAN MALAYSIA 2009 Instructions to candidates DO NOT OPEN THE BOOKLET UNTIL YOU ARE TOLD TO DO SO. There are fifty questions in this paper. For each question, four suggested answers are given. Choose one correct answer and indicate it on the multiple-choice answer sheet provided. Read the instruction on the multiple-choice answer sheet very carefully. Answer all questions. Marks will not be deducted for wrong answers. Use your own data book/sheet Arahan kepada calon:

JANGAN BUKA KERTAS SOALAN INI SEHINGGA ANDA DIBENARKAN BERBUAT DEMIKIAN. Ada LIMA puluh soalan dalam kertas ini. Bagi setiap soalan, empat cadangan jawapan diberikan. Pilih satu jawapan yang betul dan tandakan jawapan itu pada helaian jawapan aneka. Pilihan yang diberikan.. Baca arahan pada Kertas Jawapan aneka pilihan itu dengan teliti. Jawap semua soalan. Markah tidak akan ditolak bagi jawapan yang salah. Gunakan buku/helaian data sendiri.. This question paper consists of 19 printed pages and 1 blank page. Kertas soalan ini terdiri daripada 19 halaman bercetak 1 halaman kosong.

STPM TRIAL 960/1 * This question paper is CONFIDENTIAL until the examination is over. * Kertas soalan ini SULIT sehingga peperiksaan kertas ini tamat.

[Turn over/Lihat sebelah CONFIDENTIAL*/SULIT*

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1. A student measured in the length, width and height of a cubical wooden block, using a ruler with accuracy of ± 0.05 cm. He then calculated the volume of the block, and his calculator registered 108.288. Which of the following alternatives would be the best one to express his results, without losing accuracy and without including meaningless figure?

A. B. C. D.

2.

108.29 cm3 108.3 cm3 110 cm3 108 cm3

What is the dimension of thermal conductivity? B. ML-3θ-1

A. MLT-3

C. MLT-3θ-1

D. ML-3Tθ-1

3. A projectile of mass m is fired with velocity v from a point P, as shown below.

600 P

Q

Neglecting air resistance, the magnitude of the change in momentum between leaving P and arriving at Q is A. mv

B.

mv 3

C. 2 mv

D.

mv 2

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4. A body is moving with constant speed in the y-direction. For positive values of y, it experiences a uniform acceleration in the x- direction. Which one of the paths A to D does it follow?

y A. x

B.

y

x x

C.

y

x

D.

y

x

5. A ball hits the ground normally with a speed u. Which of the following is NOT TRUE if the collision is elastic?

A. B. C. D.

The particle rebounds along its original path with speed u. The momentum of the ball is conserved. The kinetic energy of the ball is conserved. The total momentum of the ball and the floor is conserved.

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6. An 5.0 kg block slides down a rough plane which is inclined at 30° as shown below.

The box starts from rest and then moves a distance of 2.0 m as measured along the incline. After it has moved this distance, its speed equals 2.0 m s-1. What is the coefficient of kinetic friction between the block and the plane? A. 0.46

B. 0.80

C. 1.04

D. 1.15

7. Two forces P and Q of the same magnitude act on a uniform metre rule pivoted at O as shown below.

P 40cm O Q Which of the following statements is TRUE? A.

The resultant forces P and Q on the metre rule is zero.

B.

Both forces P and Q exert an anti- clockwise moment about O.

C.

The moment of force P about O is greater than that of force Q about O

D. The system is in static equilibrium. 8. F

A force is applied to a regular cubical block of weight 10 N as shown above. What is the least magnitude of F required to overturn the block? A.

2N

B.

5N

C.

10 N

D.

20 N

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9. The diagram below shows a cyclist making a left turn on a rough road surface at constant speed v, as viewed from behind. The total mass of the bicycle and rider is m and their combined center of gravity is at G.

If R is the resultant force of the normal reaction and the frictional force, which vector diagram represents the directions of forces acting on the bicycle and its rider in an inertial frame?

A

C

D

B

10. A planet of mass m moves in a circular orbit of radius R round a sun of mass M with period T. Which one of the following correctly shows how T depends on m, R and M? 3

3

A.

T ∝ R 2 m2

B.

T ∝ R2M 2

3

1

C

T ∝ R2M −2

D

T ∝ R2m

1

3

−

1 2

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11. A body is released from rest at a point P a distance 3R from the centre of an isolated planet with radius R and mass M. What is the speed of the body on hitting the planet?

A.

2GM 3R

B.

GM 3R

4GM 3R

C.

2GM R

D.

12. The given diagram shows two identical bodies, represented by P, Q moving in simple harmonic motions.

If the springs are identical, the ratio of

A. 0.5

B. 0.707

Period of oscillation of Q is Period of oscillation of P

C 1.41

13. . A small mass executes s.h.m. about a point O with amplitude a T displacement from O at time after passing through O is 8 A.

a 2

B.

a 2 2

C.

a 2

D. 2

and period T. Its

D.

a 8

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14. The diagram below shows the Searle's apparatus often used in determining the Young’s Modulus of a metal. Which of the following statements NOT TRUE about the experiment ?

A. Two wires of the same material and length are hung side by side from the same clamp. B. Long and thin wire should be used so as to produce a greater extension. C. Vernier scale is used so as to measure the extension more accurately. D. The error due to thermal expansion of the wire is not taken into consideration.

15. The graph below shows how the force F between two atoms in a solid varies with the distance r between them. Which of the following statements about the distance a and b marked on the graph is CORRECT?

A. B. C. D.

The potential energy is a minimum at b. When r < b, the force is repulsive. The stiffness of the solid depends on the slope of the curve near a. Area under the graph for r > b is equal to the bonding energy.

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A vessel of volume 1x10-3 m³ contains 0.72 g of an ideal gas of O2 at a pressure of 1x105 Pa. The r.m.s. velocity of the gas molecules is

16.

A 20 m s-1

B 110 m s-1

C 340 m s-1

D 650 m s-1

17. Which of the following is NOT an assumption in deriving the kinetic theory of gases? A B C D

Attractive forces between the molecules are negligible. The volume of the molecules is negligible compared with the volume of the gas. The duration of a collision is negligible compared with the time between collisions. The molecules experience negligible change of momentum on collision with the walls of the container

18. The energy which must be supplied to 1 mole of gas initially at absolute temperature T, pressure p and volume V, to increase its temperature by 1K, is Q1 at constant pressure and Q2 at constant volume. The value of Q2 is A B C D

Q1 Q1 + pVT Q1 - pVT pV Q1 − T

19. The graph below shows the distribution of molecular speed at room temperature.

As the temperature is increased, A B C D

the peak position will move to the right and its height will increase the peak position will move to the right and its height will decrease the peak position will move to the left and its height will increase the peak position will move to the left and its height will decrease

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An ideal gas undergoes a cyclic process involving two isothermal changes and two adiabatic changes as shown in the diagram below.

Which of statements below is TRUE about the changes? A Heat is supplied to the gas and there is net work done by the gas without any increase in internal energy. B There is net heat supplied to the gas causing its internal energy to increase. C The net work done by the gas causes the internal energy to increase, but the net heat flow is zero D There is net work done on the gas causing heat to be released by the gas without any change in internal energy.

21. A glass window pane is 1.4 m high, 1.1 m wide and 3 mm thick. The temperature at the inner surface of the glass is 22°C and at the outer surface 4°C. How much heat is lost each hour through the window? (Thermal conductivity of glass = 0.812 W m-1 K-1) A. 2.7 × 107 J B. 2.7 × 104 J 3 C. 7.4 × 10 J

D. 7.4 J

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The diagram below shows a conducting sphere of radius a carries an excessive charge of + Q. An uncharged metal rod MN is brought near the sphere. The axis of the rod is collinear with a diameter through a point L on the sphere.

Which of the following graphs best illustrates the variation of potential V with distance x along their common axes?

A.

C

B.

D

23. An electron travels at speed of 1.0 x 106 m s-1 along the direction of the field lines in a uniform electric field. Its speed is reduced to zero at a distance of 4.0 x 10-2 m. What is the strength of the electric field? A. 0.71 V m-1 B. 22x103

C. 71 V m-1 V m-1

D. 22x109 V m-1

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24. A 100 μF capacitor is discharged through a resistor of resistance R. The graph below shows the variation of voltage V across the capacitor against time t.

According to the graph, what is the approximate value of R? A. 20 KΩ

35 KΩ

B

C

50 KΩ

D 200 KΩ

25. The diagram below shows three resistors of resistances 4 Ω , 10 Ω and 6 Ω connected in series. A potential difference of 10 V is maintained across them, with point Q being earthed. 10V

P

4Ω

Q

10Ω

R

6Ω

S

Which graphs represents the change in electric potential along the resistor network?

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A

C

B

D

26. The diagram below shows a cylindrical metal wire of cross-sectional area A contains n conduction electrons per cubic meter. When a potential difference is applied across the ends P and Q of the wire, electrons will drift from P to Q with a mean velocity v.

Consider the electrons in the shaded volume of length x m, which of the following statements is NOT TRUE? A. B. C. D.

The number of electrons in the shaded volume is nAx. All electrons in the shaded volume will pass through the cross-section at R in time x / v. The rate at which the conduction electrons pass through the cross- section at R is nv. The current flowing in the metal wire is given by neAv

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27. The diagram represents an aircraft of length l, wingspan x, flying horizontally at speed v in a region where the Earth’s magnetic field, of uniform flux density B, is inclined at an angle θ to the Earth’s surface.

Which expression gives the magnitude of the e.m.f. generated between the wingtips by electromagnetic induction? A.

B l v sin θ

B.

Blx

C.

Bxv

D.

B x v sin θ

28. . When a coil is rotated in a magnetic field, the induced e.m.f. E varies with time as shown in the graph below.

Which of the following graphs, drawn to the same scale, would be obtained if the speed of rotation of the coil were doubled?

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A.

B

C

D

29. An electron of mass m travels with speed v in a uniform magnetic field of strength B. The instantaneous velocity of the electron makes an angle θ with the field lines as shown in the figure.

During the time in which an electron takes to make one “twist” of the helix, what is the distance d parallel to the magnetic field made by an electron? A.

2π mv Be

B

2π mv cos θ Be

C

2 π Bev cos θ m

D.

2 π Bev sin θ m

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30. The figure below shows a thin horizontal copper plate where current I flows along the direction OS in a vertical magnetic field.

I

P Q Copper plate

O

R

S B

The Hall voltage which exists in the copper plate will produce an electric field acting along the direction A OP

B OQ

C

OR

D OS

31. A potential difference V is applied across a wire of length l and resistivity ρ. If the wire has n free electrons per unit volume, the drift velocity of the free electrons in the wire is

A

neρ Vl

B

Vρ nel

ρL C

neV

D

V neρl

32. In an ideal transformer, the most important function of the soft-iron core is A. to produce a uniform radial magnetic field in the two coils. B. to reduce the back e.m.f. produced in the coils. C. to increase the current in the coils. D. to improve the flux-linkage between the two coils.

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33. An a.c. supply is connected to a resistor. When the peak value of the e.m.f. of the supply is Vo and the frequency is f , the mean power dissipated in the resistor is P . The supply frequency is then changed to 3f , the peak value of the e.m.f. remains unchanged. What is now the mean power in the resistor? A. P

B. √3 P

C. 3P

D. 6P

34. The diagram below shows an operational amplifier.

Vi

50Ω

+

Vo 1000Ω

200Ω

What is the gain of the amplifier? A.4 B. 5 C. 6

D. 20

35. The displacement y of a point in a progressive wave with time t is given by y = 0.15 sin 4π t The wave has wavelength of 5.0 m. Determine the speed of the wave. A 2.5 m s-1

B 10 m s-1

C 63 m s-1

D 79 m s-1

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36 The graph below illustrates a transverse pulse at a certain instant which is moving towards the left along a stretched string. y P x

What is the direction of motion of point P at this instant? A B C D

Positive-x direction Negative-x direction Positive-y direction Negative-y direction

37 A point source of sound produces sound of power 500 W. What is the intensity level of sound at 5.0 m away? (Threshold intensity of hearing = 1.00x10-12 W m-2) A 122 dB

B 128 dB

C 132 dB

D 140 dB

38 The frequencies of a tuning fork and a note of a piano are f1 and f2 respectively. When both frequencies are played, beats are heard. If now a little plasticine is attached to the tuning fork, it vibrates with frequency f3. It produces beats of higher frequency with the same piano note. Which relation between the frequencies is TRUE? A f3 > f1 B f1> f2 C f1 < f2 D f3 = f2 39 The consecutive notes produced by an open pipe are 264 Hz, 352 Hz and 440 Hz. What is the frequency of the fundamental note? A 22 Hz B 44 Hz C 88 Hz D 264 Hz

40 A convex mirror has focal length f. Which statement is TRUE of the mirror? A B C D

The image size is always smaller than that of the object. Virtual image is observed only when object distance is less than f. Real image is observed when object distance is greater than f. The image size is the same as that of the object when the object distance is 2f.

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41 Which electromagnetic wave has frequency in the order of 1.0 x 1016 Hz? A Radio wave

B microwave

C visible light

D ultraviolet

42 The lens of a sunglasses is made up of lamination of two polarisers with its axis of polarisation making an angle of 30o . What is the percentage of the intensity of the incident light transmitted? A 37 %

B 43%

C 57%

D 63 %

43 Two loudspeakers separated by a short distance produces sound of the same frequency. At a position in front of the speakers, the path difference from the position to each of the speakers is 1.2 m. At that position, maximum loudness is heard when the frequency is 1000 Hz and the next maximum is heard when the frequency is increased to 1200 Hz. What is the speed of sound based on the observation? A 120 m s-1

B 240 m s-1

C 300 m s-1

D 340 m s-1

44 A converging lens of focal length 12.0 cm forms an upright image three times the size of the object. The distance between the object and the image is A 16.0 cm B 32.0 cm C 48.0 cm D 64.0 cm

45 The diagram below show the air wedge formed by inserting a thin piece of paper at the edge of two slide glasses. Paper

When monochromatic light is incident normally from above, interference pattern is observed. The fringe separation becomes narrower when A B C D

thinner paper is used the paper is pulled further to the edge monochromatic light of longer wavelength is used the air wedge is replaced with water to form the water wedge

46 Sodium lamps emit light strongly at two very closely wavelengths. There are the “sodium-D lines” at 589.0 nm and 589.6 nm. If a diffracting grating with 500 lines per mm is used, calculate the angular separation between the first order spectra lines due to these wavelengths? A 0.017o B 0.018o C 17.13o D 17.15o

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47. A photocathode whose work function is 2.7 eV is illuminated with white light that has a continuous wavelength band from 400 nm to 700 nm. The range of the wavelength band in this white light illumination for which photoelectrons are not produced is A. 460 nm to 700 nm B. 400 nm to 520 nm C. 460 nm to 520 nm D. 520 nm to 700 nm

48. Characteristic x-rays can be produced by bombarding targets with electrons. These x-rays occur when A B C D

electrons from higher shells fill the vacant lower shell electrons fill the vacant valence shell electrons decelerate and radiate energy electrons transfer all their kinetic energy to the target atoms.

49. For stable nuclei with large mass number, the ratio of protons to neutrons is A equal to 1 B. greater than 1 C less than 1 D. unrelated to the stability of nuclei

50. Find the binding energy of carbon-12. Assume: mC = 11.996706 u mp = 1.007276 u mn = 1.008665 u u = 1.66 × 10–27 kg A B. C. D.

0.511 MeV 9.11 MeV 14.8 MeV 92.3 MeV

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STPM TRIAL 2009

PHYSICS (FIZIK)

PAPER 2 ( KERTAS 2)

STRUCTURE AND ESSAY (STRUKTUR DAN ESEI)

Instruction to candidates: DO NOT OPEN THE BOOKLET UNTIL YOU ARE TOLD TO DO SO. Answer all the que stions i n s ection A i n t he s paces pr ovided. A ll working must be shown. For calculation, relevant values of constants in the dat a book let must be us ed. F or num erical answers, uni t must be quoted whenever they are appropriate. Answer any four questions from section B. For this section, write your answers on t he ans wer sheets pr ovided. Begin each ans wer on a f resh sheet of paper, and arrange your answers in numerical order. Tie your answer sheets to this booklet. Answer may be written in either English or Malay. Arahan kepada calon:

JANGAN BUKA KERTAS SOALAN INI DIBENARKAN BERBUAT DEMIKIAN.

SEHINGGA ANDA

Jawab semua soalan dalam b ahagian A da lam r uang y ang d isediakan.. Semua k erja mestilah ditunjukkan. Bagi pe nghitungan nilai p emalar y ang berkaitan dalam Buku Data mestilah digunakan. Bagi jawapan berangka, unit mestilah dinyatakan di mana-mana yang sesuai. Jawap mana-mana empat soalan. dalam bahagian B. Untuk bahagian ini, tulis jawapan andapada helaian yang dibekalkan. . Mulakan setiap j awapan pada h elaian k ertas y ang ba ru, dan s usun jawapan anda mengikut t ertib be rangka. I kat k ertas j awapan and a be rsama de ngan k ertas soalan ini. Jawapan boleh ditulis dalam bahasa Inggeris atau bahasa Melayu.

For examiner’s use (Untuk kegunaan pemeriksa) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Total (Jumlah)

This question paper consists of 13 printed pages and 1 blank page. (Kertas soalan ini terdiri daripada 13 halaman bercetak dan 1 halaman kosong.) 960/2 * This question paper is CONFIDENTIAL until the examination is over. *Kertas soalan ini SULIT sehingga peperiksaan kertas ini tamat.

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2 Section A [ 40 marks ] Answer all the questions in this section.

1. (a) Explain what is meant by work and power.

(b)

[2]

A car of mass 1540 kg is moving up a slope making an angle of 30o with the horizontal. The total air resistance acting on the car is 500N. If the car is moving at a constant speed of 20.0 m s-1, (i) calculate the force exert by the engine. [2]

(ii) find the power of the engine.

[2]

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2. A uniform beam having a mass of 60 kg and a length of 2.8 m is held in place at its lower end by a pin. Its upper end leans against a vertical frictionless wall as shown in the figure. (a) In the diagram below, show the direction of reaction forces acting on the beam and the weight of the beam. [3]

40o

(b) What is the magnitude of the force the pin exerts on the beam?

[3]

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Based on a thermodynamic law, explain the drop in the temperature of a gas during an adiabatic expansion. [2]

(b) The following p-V graph represents a cyclic process in an ideal gas of constant mass. The overall process is represented by three separate changes I, II and III. P

i) Identify which change represents adiabatic change?

[1]

ii) If the above processes represents the changes in a heat engine, in what sequence must the three processes take place? Explain how you deduce your answer. [2]

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(a) A sound source of a certain frequency moving towards a stationary observer. The frequency of the sound heard by the observer is different from that of the source. Explain this phenomenon in terms of change in wavelength, frequency and velocity. [3 ]

(b) A car traveling normally towards a cliff at a speed of 30 m s-1 sounds its horn which emits a note of frequency 100 Hz. What is the frequency of the echo as heard by the driver? (Speed of sound is 330 m s-1. ) [3]

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5. (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. E having negligible internal resistance. E

(i) Sketch graphs to show the time variation of the voltage across the capacitor and the current in the circuit after closing switch S. [2]

(ii) 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. [3]

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6. You are given some isotopes of a certain element. The isotopes are ionized so that they can carry the same charge Q, and enter a speed selector as shown in the diagram below. Only those isotopes with a definite speed can pass straight through the mutually perpendicular uniform electric and magnetic fields in the speed selector. The whole set-up is in a vacuum environment.

(i) Explain how the speed selector works.

[2]

(ii) Describe and explain how the isotopes can be distinguished experimentally by directing the emerging beam of ionized isotopes into a uniform magnetic field. [3]

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7. The diagram below shows two point charges, A and B, separated by a distance of 1.20 m QA = –1.50 × 10-6 C and QB = +4.20 × 10-6 C

(a) Calculate the magnitude and direction of electric field at point P, midway between the charges. [3]

(b) Calculate the electric potential at point P.

[2]

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8. In an X-ray tube, electrons are accelerated towards an anode by a potential difference of 10,500 V.

(a) Calculate the de Broglie wavelength of the electrons just before collision with the anode. [3]

(b) Calculate the minimum wavelength in the X-ray continuous spectrum.

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10 Section B [ 60 marks ] Answer any four questions in this section.

9. (a) State Newton’s Law of Universal Gravitation.

[1]

(b) A satellite of mass 200 kg is placed in a circular orbit at a height of 200 km above the Earth’s equator travelling in the same direction as the rotation of Earth about its own axis. (i) Explain why the centre of the orbit must be at the centre of the Earth.

[2]

(ii) Calculate the speed of the satellite.

[3]

(iii) The satellite passes a particular place on the ground at certain time of the day, by taking into account the rotation of the Earth, find the time interval it will pass the same place again ? [4] (iv) By ignoring air resistance, calculate the minimum energy required to launch the satellite into its orbit from the ground. [3] (v) What is the minimum speed of the satellite in the orbit so that it can escape from the gravitational field of the Earth and travel to infinity. [2] (Radius of Earth R = 6.40x106 m) 10. a) The pressure p of an ideal gas of density ρ is related to the mean-square speed of its molecules by the expression

i) State three basic assumptions of the kinetic theory of gases, which lead to a model of an ideal gas [3] ii) Write down the equation for an ideal gas. Explain the symbols you use. [2] iii) Show that the average kinetic energy of a molecule of an ideal gas is proportional to the thermodynamic temperature T. [4 ] b) A tank contains 2.0 moles of helium gas at 200C. The molar mass of helium is 4.0 g. Assume that the helium gas behaves as an ideal gas i) find the total internal energy of the system

[2]

ii) what is the average kinetic energy per molecule

[2]

iii) determine the r.m.s. speed of the helium atoms at 200C.

[2]

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(a) State the phenomenon which proved that light is a transverse wave? (b) The diagram below shows a charge oscillating along the y-axis.

[1 mark]

y

Charge

x

z The oscillating charge produces an EM wave propagating in the positive-z direction. State the respective axis in which the oscillations of the electric field component E and the magnetic field component B of the wave. [2 ] (c) The light from a light bulb is a unpolarized light. Explain. [2 ] (d) The polarizing material consists of parallel long straight chain molecules. When unpolarized light passing through it, the light transmitted will be polarized light. (i) State the direction of the polarizing axis referring to the long straight chain molecules. [1 ] (ii) Explain what happens when an EM wave passes through these long straight chain molecules. [2 ] (iii) If the electric field component of the EM wave is lost, what happens to the magnetic field component? [1 ] (e) The diagram below shows an unpolarized light of intensity Io passing through two polarizers. θ

Polarizing axis

(i) State the intensity of light after passing through the first polarizer in terms of Io and explain your answer [3 ] (ii) Calculate the angle θ if the light emitted from the two polarizers has intensity 25% that of the incident light. [3 ]

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12. (a) Explain what is meant by mutual inductance between two coils.

[1]

(b) A large long solenoid is made with 60 turns per centimeter. A smaller solenoid has 30 turns, is 2.0 cm long and has a diameter of 0.80 cm. The ends of the small solenoid are connected to a 10 Ω resistor. The small solenoid is placed right in the centre of the large solenoid. In the di agram below the small solenoid is shown outside the large solenoid for clarity. The large solenoid is then connected to a DC power supply which changes the current in the large solenoid from zero to 10 A in a time of 2.0 ms.

I

10 Ω

Power Supply

i) Calculate the magnitude of the magnetic field in the large solenoid when the current is at its maximum value of 10 A. [2] ii) Calculate the average current passing through the 10 Ω resistor while the current in the large solenoid is changing. [3] iii) If the direction of the current in the large solenoid is as shown in the diagram, in which direction does current go in the resistor (to the left or to the right)? [1] iv) Calculate the mutual inductance of the two coils.

[3]

(c) An AC motor of an electric drill has a resistance of 13.0 Ω. When it is turning at its maximum speed it draws an rms current of 2.10 A when connected to a 120 V rms supply. i) Calculate the back emf when the drill is running at its maximum speed. [2] ii) Calculate the rms current drawn by the drill when it is drilling through some hardwood at one quarter of its maximum speed. [3]

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13 (a) State the difference between X-rays and γ-rays.

[2]

(b) (i) Sketch a graph to show the variation of the intensity with wavelength for the Xray spectra obtain at two different voltages V1 and V2 (V1 < V2 ) from an X-ray tube. [2] (ii) Explain how the continuous spectrum and the characteristic line spectrum of Xrays are formed. [4] (c) The K series of the discrete X-ray spectrum of tungsten contains wavelengths of 0.0209 nm (transition from L to K shell) , and 0.0215 nm (transition from M to K shell). The K-shell ionization energy is 69.5 keV. (i) Draw a diagram of the transitions. [2] (ii) Determine the ionization energies of the L and M shell. [5]

14. (a) Potassium-40 is a radioactive isotope of potassium which is present in human body. The main decay mode is for 1940 K to decay by the emission of a beta particle to produce the stable product of 2040 Ca . Write an equation for this radioactive decay process.

[1]

(b) Calculate the energy emitted in Joule when one nucleus of 1940 K undergoes the above decay process. Explain why the mass of beta particle is not considered in your calculation. [5] (c) 0.3% of the human body mass is potassium of which only 0.0117% of the potassium are isotope 1940 K . Calculate the number of isotope 1940 K atoms per kilogram of the human body. [2] (d) If the half life of 1940 K is 1.28x109 years, calculate the rate of decay of kilogram in the human body.

40 19

K in Bq per [4]

(e) One third of the energy of each decay is deposited in the body. Calculate the total energy absorbed by a boy of mass 40 kg in one year. [3]

Given : The mass of one The mass of one

40 19

K atom = 39.964000 u

40 20

Ca atom = 39.962591 u

-----------------------------------------END--------------------------------------------------------------

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CONFIDENTIAL* Identity card number:…………….………………..…..

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(Nombor kad pengenalan) PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA Two and a half hours (Dua jam setengah) PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA-PENGETUA PERSIDANGANKEBANGSAANPENGETUA PENGETUA PERSIDANGANKEBANGSAANPENGETUA PENGETUA

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STPM TRIAL 2009

PHYSICS (FIZIK)

PAPER 2 ( KERTAS 2)

STRUCTURE AND ESSAY (STRUKTUR DAN ESEI)

Instruction to candidates: DO NOT OPEN THE BOOKLET UNTIL YOU ARE TOLD TO DO SO. Answer all the que stions i n s ection A i n t he s paces pr ovided. All working must be shown. For calculation, relevant values of constants in the dat a book let must be us ed. F or num erical answers, uni t must be quoted whenever they are appropriate. Answer any four questions from section B. For this section, write your answers on t he ans wer sheets pr ovided. Begin each ans wer on a f resh sheet of paper, and arrange your answers in numerical order. Tie your answer sheets to this booklet. Answer may be written in either English or Malay. Arahan kepada calon:

JANGAN BUKA KERTAS SOALAN INI DIBENARKAN BERBUAT DEMIKIAN.

SEHINGGA ANDA

Jawab semua soalan dalam b ahagian A da lam r uang y ang d isediakan.. Semua k erja mestilah ditunjukkan. Bagi pe nghitungan nilai p emalar y ang berkaitan dalam Buku Data mestilah digunakan. Bagi jawapan berangka, unit mestilah dinyatakan di mana-mana yang sesuai. Jawap mana-mana empat soalan. dalam bahagian B. Untuk bahagian ini, tulis jawapan andapada helaian yang dibekalkan. . Mulakan setiap j awapan pada h elaian kertas y ang ba ru, dan s usun jawapan anda mengikut t ertib be rangka. I kat k ertas j awapan and a be rsama de ngan k ertas soalan ini. Jawapan boleh ditulis dalam bahasa Inggeris atau bahasa Melayu.

For examiner’s use (Untuk kegunaan pemeriksa) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Total (Jumlah)

This question paper consists of 13 printed pages and 1 blank page. (Kertas soalan ini terdiri daripada 13 halaman bercetak dan 1 halaman kosong.) 960/2 * This question paper is CONFIDENTIAL until the examination is over. *Kertas soalan ini SULIT sehingga peperiksaan kertas ini tamat.

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Section A [ 40 marks ] Answer all the questions in this section. 1. (a) Explain what is meant by work and power.

(b)

[2]

  Work W = F • s F = Force S = displacement

(1)

Power is the rate of doing work.

(1)

A car of mass 1540 kg is moving up a slope making an angle of 30o with the horizontal. The t otal a ir r esistance acting on t he c ar i s 500 N. If t he c ar i s m oving at a constant speed of 20.0 m s-1, (i) calculate the force exert by the engine. [2] F = mgsinθ + R

(1)

= 540x9.81xsin30o + 500 = 8054 N

(1)

(ii) find the power of the engine. P = Fv

(1)

= 1.61x105 W (1) [2]

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2. A uniform beam having a mass of 60 kg and a length of 2.8 m is held in place at its lower end by a pin. Its upper end leans against a vertical frictionless wall as shown in the figure. (a) In the diagram below, show the direction of reaction forces acting on the beam and the weight of the beam. [3]

R2 R1

W 40o

One mark for each direction. (b) What is the magnitude of the force the pin exerts on the beam?

[3]

Consider moment of forces about the pin : R1x2.8sin40o = Wx1.4cos40o

(1)

R1 = 350.7 N R2y = W = mg = 588.6 N

{1}

R2x = R1 = 350.7 N

(1)

2

2

R2 = R2 x + R2 y = 685 N

(1)

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3. a)

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Based on a t hermodynamic l aw, explain the dr op in the t emperature of a ga s during an adiabatic expansion. [2] In an adiabatic expansion, no heat is absorbed or released by the system. (1) Therefore w ork i s done by us ing t he i nternal energy and t hus t he t emperature decreases. (1) Or From Q = dU + W Q=0

(1)

W = - dU ; thus temperature decreases.

(1)

(b) The following p-V graph represents a cyclic process in an ideal gas of constant mass. The overall process is represented by three separate changes I, II and III. P

i) Identify which change represents adiabatic change?

[1]

II ii) If the above processes represents the changes in a heat engine, in what sequence must the three processes take place? Explain how you deduce your answer. [2] II  I  III

or clockwise

(1)

So that there is a net work done by the system.

(1)

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4.

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(a) A s ound s ource of a c ertain f requency moving t owards a s tationary obs erver. T he frequency o f t he s ound he ard by t he obs erver i s di fferent from t hat of t he s ource. Explain this phenomenon in terms of change in wavelength, frequency and velocity. [3 ] The apparent wavelength decreases. (1) But the velocity of the wave is unchanged.

(1)

From the equation , f = v/λ When the wavelength decreases, the apparent frequency increases. (1)

(b) A car traveling normally towards a cl iff at a s peed of 30 m s -1 sounds its horn which emits a note of frequency 100 Hz. What is the frequency of the echo as heard by the [3] driver? (Speed of sound is 330 m s-1. )

v+u f '=  f v−u  330 + 30  =  x100  330 − 30  = 120 Hz

1 1 1

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5. (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. E having negligible internal resistance. E

(i) Sketch graphs to show the time variation of the voltage across the capacitor and the current in the circuit after closing switch S. [2]

I

V

(1) (1) 0

t

t 0

(ii) With switch S closed, the plates of the capacitor are pulled apart slightly. Describe and explain t he pos sible c hange(s) i n t he c harge a nd t he e nergy stored i n t he c apacitor when the steady state is reached. [3] The charge decreases. (1) The energy stored also decreases. (1) Because the capacitance decreases but the potential difference is unchanged. (1)

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6. You are given some isotopes of a certain element. The isotopes are ionized so that they can carry the same charge Q, and enter a speed selector as shown in the diagram below. Only those isotopes with a definite speed can pass straight through the mutually perpendicular uniform electric and magnetic fields in the speed selector. The whole set-up is in a vacuum environment.

(i) Explain how the speed selector works.

[2]

In the speed selector, the electrostatic force and the magnetic force acting the charged particle are equal in magnitude but opposite in direction. (1) Therefore the resultant force is zero, thus the charge will move in a straight line. (1) Or

qE = Bqv ∑F=0

or

FE = FB

(1)

(1)

(ii) Describe and explain how the isotopes can be distinguished experimentally by directing the emerging beam of ionized isotopes into a uniform magnetic field. [3] Different isotopes will be deflected in magnetic field in semicircular path of different radii. (1, 1) The mass of the isotope is directly proportional to the radius of the path. (1) Or

Bqv = mv2/r mα r

(1) (1)

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7. The diagram below shows two point charges, A and B, separated by a distance of 1.20 m QA = –1.50 × 10-6 C and QB = +4.20 × 10-6 C

(a) Calculate the magnitude and direction of electric field at point P, midway between the charges. [3] Direction : BA

EP =

=

QA 4πε o r1

2

(1)

QB

+

4πε o r2

(1)

2

1.5 x10 −6 4.2 x10 −6 + = 1.42 x10 5 Vm −1 4πε o (0.6) 2 4πε o (0.6) 2

(1)

(b) Calculate the electric potential at point P.

VP =

QA

4πε o r

+

QB

4πε o r

= 4.05 x10 4 V

[2]

(1)

(1)

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8. In an X-ray tube, electrons are accelerated towards an anode by a potential difference of 10,500 V. (a) Calculate the de Broglie wavelength of the electrons just before collision with the anode. [3] 1 2

mv 2 = eV

(1)

2eV = 6.073 x10 7 m h λ= (1) p

v=

= 1.20 x10 −11 m s −1

(1)

(b) Calculate the minimum wavelength in the X-ray continuous spectrum.

hc

λ

= eV

λ = 1.18 x10 −10 m

(1) (1)

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[2]

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Section B [ 60 marks ] Answer any four questions in this section. 9. (a) State Newton’s Law of Universal Gravitation.

[1]

The gravitational attraction between two point masses is directly proportional to the product of the masses but inversely proportional to the square of their separation. (b) A satellite of mass 200 kg is placed in a circular orbit at a height of 200 km above the Earth’s equator travelling in the same direction as the rotation of Earth about its own axis. (i) Explain why the centre of the orbit must be at the centre of the Earth. The weight of the satellite provides the centripetal force.

[2]

(1)

Since the weight acts towards the centre of the Earth, therefore the centre of the Earth is the centre of the orbit. (1) (ii) Calculate the speed of the satellite. mv 2 GMm = r r2 v=

=

gR 2 r

[3]

(1) GM = gR 2

(1)

9.81x(6.4 x10 6 ) 2 6.6 x10 6

= 7800m / s

(1)

(iii) The satellite passes a particular place on the ground at certain time of the day, by taking into account the rotation of the Earth, find the time interval it will pass the same place again ? [4] v = rw

(1)

7800 = 1.182 x10 −3 rad s −1 6.6 x10 6 2π Angular velocity of Earth ω ' = (1) T = 7.27 x10 −5 rad s −1

ω=

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Relative angular velocity ω r = ω − ω '

(1)

= 1.109 x10 −3 rad s −1 T=

2π

ωr

= 5660 s

(1)

(iv) By ignoring air resistance, calculate the minimum energy required to launch the satellite into its orbit from the ground. [3] W = ∆U + E K

(1)

GMm GMm 1 2 − + 2 mv R r  1 1 = gR 2 m −  + 12 mv 2 R r =

(1)

1 1  = 9.81(6.4 x10 6 ) 2 x 200 − 6 6.6 x10 6  6.4 x10 = 6.47 x10 9 J

 1 2  + 2 x 200 x7800  (1)

(v) What is the minimum speed of the satellite in the orbit so that it can escape from the gravitational field of the Earth and travel to infinity. [2] (Radius of Earth R = 6.40x106 m) 1 2

mv 2 = v=

GMm r

(1)

2 gR 2 r

= 1.10 x10 4 m s −1

(1)

10. a) The pressure p of an ideal gas of density ρ is related to the mean-square speed of its molecules by the expression

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i) State three basic assumptions of the kinetic theory of gases, which lead to a model of an ideal gas [3] Any three of the followings: The gas molecules move randomly in all direction. The collisions between the molecules and the wall of the container are elastic. There is no force between the molecules. The time of collision can be neglected compared to the time between collisions. The motion of gas molecules obeys Newton’s Laws of motion. The volume of the molecules can be neglected compared to the volume of the container.

-

ii) Write down the equation for an ideal gas. Explain the symbols you use. [2] pV = nRT p = pressure of gas V = volume n = number of mole of gas T= temperature in Kelvin

2/0

iii) Show that the average kinetic energy of a molecule of an ideal gas is proportional to the thermodynamic temperature T. [4 ]

1 Nm < c2 > 3 V 3PV m < c 2 >= N 3nRT = N 3nRT = nN A P=

1 3RT m < c 2 >= 2 2N A =

3 kT 2

(1)

(1)

(1)

(1)

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b) A tank contains 2.0 moles of helium gas at 200C. The molar mass of helium is 4.0 g. Assume that the helium gas behaves as an ideal gas i) find the total internal energy of the system

[2]

(1)

f nRT 2 3 = × 2 × 8.31 × 293 2 = 3704 J

U=

(1)

ii) what is the average kinetic energy per molecule

[2]

(1)

3 kT 2 = 6.07 × 10 − 21 J

EK =

(1)

iii) determine the r.m.s. speed of the helium atoms at 200C. 1 m < c 2 >= 6.07 × 10 − 21 2 1 4 × 10 −3 × < c 2 >= 6.07 × 10 − 21 2 6.02 × 10 23 2

< c > = 1350ms 11.

[2]

(1) (1)

−1

(a) State the phenomenon which proved that light is a transverse wave?

[1 mark]

Polarization of light (b) The diagram below shows a charge oscillating along the y-axis. y

Charge

x

z The oscillating charge produces an EM wave propagating in the positive-z direction. State the respective axis in which the oscillations of the electric field component E and the magnetic field component B of the wave. [2 ] 960/2

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Electric field : along y-axis Magnetic field : along x – axis.

(1) (1)

(c) The light from a light bulb is a unpolarized light. Explain. Emission of light is a random/spontaneous process.

[2 ] (1) (1)

Plane of oscillation is random.

(d)

The pol arizing material consists of pa rallel long s traight c hain molecules. When unpolarized light passing through it, the light transmitted will be polarized light. (i) State the di rection of the pol arizing axis r eferring to the lon g straight cha in molecules. [1 ] The polarizing axis is perpendicular to the molecular chain. (ii) Explain what happens when an EM wave passes through these long straight chain molecules. [2 ] If electrical oscillations is parallel to the chain molecules, the electrical energy will be absorbed. (1) If the electrical oscillations is perpendicular to the chains molecules, it will pass through. (1) Or The em wave will be polarized in the plane perpendicular to the chain molecule (2) (iii) If the electric field component of the EM wave is lost, what happens to the magnetic field component? [1 ] The magnetic field component will be lost too.

(e) The diagram below shows an unpolarized light of intensity Io passing through two polarizers. θ

Polarizing axis

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(i) State the intensity of light after passing through the first polarizer in terms of Io and explain your answer [3 ] 1 1 Io . 2 The EM oscillations can be resolved into two perpendicular directions. The component which is parallel to the polarizing axis passes through

1 1

(ii) Calculate the angle θ if the light emitted from the two polarizers has intensity 25% that of the incident light. [3 ] I1 =

1 Io 2

I 2 = I 1 cos 2 θ 1 0.25Io = I o cos 2 θ 2 θ = 45o

1 correct substitution of I2 and I1

1 1

12. (a) Explain what is meant by mutual inductance between two coils. Mutual inductance M = - Induced emf in secondary coil Rate of change of current in primary coil

[1] (1)

(b) A large long solenoid is made with 60 turns per centimeter. A smaller solenoid has 30 turns, is 2.0 cm long and has a diameter of 0.80 cm. The ends of the small solenoid are connected to a 10 Ω resistor. The small solenoid is placed right in the centre of the large solenoid. In the di agram b elow the small solenoid is shown outside the large solenoid for clarity. The large solenoid is then connected to a DC power supply which changes the current in the large solenoid from zero to 10 A in a time of 2.0 ms.

I

10 Ω

Power Supply

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i) Calculate the magnitude of the magnetic field in the large solenoid when the current is at its maximum value of 10 A. [2] B = μonI

(1)

= 4πx10-7x60x102x10 = 0.0754 T

(1)

ii) Calculate the average current passing through the 10 Ω resistor while the current in the large solenoid is changing. [3] dΦ dt NBA =− t NBA IR = − t E=−

I =−

(1) E = IR

(1)

NBA 30 × 0.0754 × π (0.40 × 10 − 2 ) 2 = ( −) Rt 10 × 2 × 10 −3 = 5.685mA or 5.7 mA

(1)

iii)

If the direction of the current in the large solenoid is as shown in the diagram, in which direction does current go in the resistor (to the left or to the right)? [1] To the right

iv)

Calculate the mutual inductance of the two coils. [3]

Es = − M IR = M

dI p dt

dI p dt

10 2 ×10 −3 M = 1.137 ×10 −5 H or 1.1×10 −5 H

5.685 ×10 −3 ×10 = M Or

(1)

Φ s = MI p

(1) (1) (1)

NBA = MI P 30 × 0.0754 × π (0.80 ×10 −2 ) = M ×10

(1)

M = 1.14 ×10 −5 H

(1)

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(c) An AC motor of an electric drill has a resistance of 13.0 Ω. When it is turning at its maximum speed it draws an rms current of 2.10 A when connected to a 120 V rms supply. i) Calculate the back emf when the drill is running at its maximum speed. [2] (1)

V − Eb = Ir 12 − Eb = 2.1 × 13 Eb = 92.7V

(1)

ii) Calculate the rms current drawn by the drill when it is drilling through some hardwood at one quarter of its maximum speed. [3] Eb ∝ f

(1)

1 × 92.7 = 23.18V 4 V − Eb' = I ' r Eb' =

(1)

12 − 23.18 = I ' × 13 I ' = 7.45 A

(1)

13 (a) State the difference between X-rays and γ-rays.

[2]

X-ray is produced by transition of electron in atom

(1)

γ –ray is produced by radioactive decay of a nucleus or in nuclear reaction. (1) (b)

(i) Sketch a graph to show the variation of the intensity with wavelength for the Xray spectra obtain at two different voltages V1 and V2 (V1 < V2 ) from an X-ray tube. [2] Intensity, I 1 mark for each graph with at least one characteristic line

V2 V1 0

λ

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(ii) E xplain how the continuous spectrum and the characteristic line spectrum of Xrays are formed. [4] Continuous s pectrum i s pr oduced w hen an e lectron bom barding t he a node t arget experiences deceleration. (1) Kinetic energy of the electron is changed into photon or radiated as electromagnetic wave. (1) The line spectrum is produced by transition of electron from higher energy level to the innermost orbit in the anode atom. (1) The ene rgy di fference be tween t he t wo or bits i s r adiated as a phot on of di screte wavelength. (1) (c) The K series of the discrete X-ray spectrum of tungsten contains wavelengths of 0.0209 nm (transition from L to K shell) , and 0.0215 nm (transition from M to K shell). The K-shell ionization energy is 69.5 keV. (i) Draw a diagram of the transitions. [2] N M

EM

L

EL

K

0.0209 nm 0.215 nm

1 mark for each transition

-69.5 KeV

(ii) Determine the ionization energies of the L and M shell.

[5]

For transition L  K : ∆E = E L − (−69.5) ∆E =

(1)

keV

hc

(1)

λ

[E L + 69.5]× 10 3 × 1.6 × 10 −19 = E L = −11.68 KeV

hc 0.0215 × 10 −9

eV J

(1) (1)

Ionization energy of L shell = 11.68KeV For transition M K : EM = - 10.02 KeV Ionization energy of M shell = 10.02 KeV

(1)

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14. (a) Potassium-40 is a radioactive isotope of potassium which is present in human body. The main decay mode is for 1940 K to decay by the emission of a beta particle to produce the stable product of 2040 Ca . Write an equation for this radioactive decay process. 40 19

40 K → 20 Ca +

0 −1

e

[1] (1)

(b) Calculate the energy emitted in Joule when one nucleus of 1940 K undergoes the above decay process. Explain why the mass of beta particle is not considered in your calculation. [5] (1)

∆m = 39.964000 − 39.962591 = 1.409 × 10 −3 u E = ∆m c 2

(1) −3

= 1.409 × 10 × 1.66 × 10 = 2.105 × 10

−13

− 27

8 2

× (3.0 × 10 )

J or 2.11 × 10 −13 J

(1)

The 1940 K atom contains 19 electrons while 2040 Ca atom contains 20 electrons. (1) Therefore the mass of electron (beta particle) has been taken into consideration. (1) (c) 0.3% of the human body mass is potassium of which only 0.0117% of the potassium are isotope 1940 K . Calculate the number of isotope 1940 K atoms per kilogram of the human body. [2] Mass of

40 19

Number of

K per kg = 0.3% x 0.0117% = 3.51x10-7 kg 40 19

K atoms per kg =

(1)

3.51 × 10 −7 × 6.02 × 10 23 −3 40 × 10

= 5.283x1018

(1)

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(d) If the half life of 1940 K is 1.28x109 years, calculate the rate of decay of kilogram in the human body.

40 19

K in Bq per [4]

(1)

dN = λN dt ln 2 λ= T1 / 2

(1)

ln 2 dN = × 5.283 × 1018 9 dt 1.28 × 10 × 365 × 24 × 3600 = 90.72 Bq or s −1

Change yr  s (1) (1)

(e) One third of the energy of each decay is deposited in the body. Calculate the total energy absorbed by a boy of mass 40 kg in one year. [3]

Given : The mass of one The mass of one

40 19

K atom = 39.964000 u

40 20

Ca atom = 39.962591 u

E = 90.72 × (365 × 24 × 3600) × 40 × 2.105 × 10 −13 Energy absorb =

(1, 1)

1 E 3 (1)

= 8.03 × 10 −3 J

-----------------------------------------END-------------------------------------------------------------PHYSICS PAPER 1 2009 MALACCA STATE TRIAL EXAM MARKING SCHEME : 1D 2C 3B 4C 5B 6A 7A 8B 9A 10C

11C 12C 13A 14D 15C 16D 17D 18D 19B 20A

21A 22B 23C 24C 25A 26C 27D 28A 29B 30C

31D 32D 33A 34C 35B 36D 37A 38C 39C 40A

41D 42A 43B 44A 45D 46B 47A 48A 49C 50D

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