Stpm Trial 2009 Phy Q&a (n9)

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JAWATANKUASA PANEL TRIAL EXAM PHYSICS STPM NEGERI SEMBILAN DARUL KHUSUS

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960 PHYSICS STPM Values of constants

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Speed of light in free space

c = 3.00 x 108 ms-1

Permeability of free space

µo = 4π x 10-7 Hm-1

Permittivity of free space

εo = 8.85 x 10-12 Fm-1

Magnitud of electronic charge

e = 1,60 x 10-19 c

Plank 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-1 mol-1

Avogadro constant

NA = 6.02 x 1023 mol-1

Boltzmann constant

K = 1.38 x 10-23 JK-1

Gravitational constant

G = 6.67 x 10-11 Nm2 Kg-2

Acceleration of free fall

g = 9.81 ms-2

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1. The ratio of electric field strength has a unit which is the same as that of magnetic flux density A force

B energy

C velocity

D acceleration

2. An aluminium ball P and an iron ball Q of the same volume are thrown horizontally with the same velocity from the top of a building. Neglecting air resistance, P reaches the ground A B C D

before Q and at the same distance from the building. at the same time as Q and at a nearer distance to the building. at the same time as Q and at the same distance from the building as Q. after Q and at the same distance from the building.

3. Two blocks of wood, X and Y of masses 30 g and 40 g respectively are placed so that they touch each other on a smooth horizontal surface. A horizontal force of 35 N is applied on block X so that both blocks accelerate together.

Find the horizontal force acting on block Y A 0N

B 15 N

C 20 N

D 35 N

4. A trolley is pulled along a smooth horizontal track by a constant force. Which of the following graphs best describes the variation of the trolley’s kinetic energy E with time t if air resistance is negligible?

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5. A body X of mass m and a body Y of mass 3m move in circles of radius 2r and r respectively. If the circles have the same centre O and X and Y are always collinear, what is the value of the ratio of centripetal force on X/ centripetal force on Y? A 1:6

B 2:3

C 3:4

D 3:2

6. When a body moves with constant speed in a circular path, the quantity which varies with time is A B C D

moment of inertia linear momentum angular momentum angular velocity

7. Which of the following does not affect the moment of inertia of a rotating rigid body? A B C D

Mass Shape Angular acceleration Mass distribution

8. The diagram shows a diving board held in position by two rods, X and Y.

5m X Y 2m

750 N

Find the additional forces which act on the board when a diver of 750 N stands on the right hand end.

A B C D

At X (Downwards) 900 N 1125 N 1375 N 1375 N

At Y (Upwards) 1500 N 1875 N 1875 N 1500 N

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9. A man-made satellite is shifted from a stable circular orbit to another lower but equally stable orbit. Which of the following quantities decreases? A B C D

Gravitational potential energy Orbital linear speed Centripetal acceleration Kinetic energy

10. A mass of 0.20 kg is connected to a helical spring which experiences simple harmonic motion of period 1.0 s. By how much must the original mass be reduced if the period of oscillation is to be reduced to 0.8 s? A 0.035 kg

B 0.040 kg

C 0.060 kg

D 0.070 kg

11. A stationary wave in a stretched string are represented by the equation

π

x cos 20πt , with x and y in centimeter, and t in s. What is the 4 distance between two consecutive nodes in the stationary waves? y = 2 sin

A 2.0 cm

B 4.0 cm

C 6.0 cm

D 8.0 cm

12. A standing wave of 603 Hz is produced on a string that is 1.33 m long and fixed on both ends. If the speed of waves on the string is 402 ms-1, how many antinodes are there in the standing wave? A 1

B 2

C 3

D 4

13. At a distance 20 m from a loudspeaker, the amplitude of the sound heard is 0.012 mm. At a distance 30 m from the loud speaker, the amplitude in mm is A 0.008

B 0.012

C 0.018

D 0.024

14. A pipe closed at one end is resonating to its first overtone. Which of the following diagram shows the vibrations of the air in the pipe at four equally spread points? A

B

C

D

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15. The physical phenomenon not observable for sound waves is A reflection

B refraction

C inteference

D polarization

16. The figure below shows a graph of potential energy U against intermolecular distance r for a diatom.

Which of the following is true for the intermolecular forces at point P and at point Q? Point P A B C D

Point Q

Attraction Zero Zero Repulsion

Zero Attraction Repulsion Zero

17. Which of the shades areas from the graphs below represents the amount of strain energy per unit volume stored in a wire when the wire is loaded? Force

Stress

Strain

0

Extension

0

A

B

Stress

Strain

0 C

Extension

0 D

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18. The figure below shows a glass rod of diameter 2r. One end of the rod has a surface which is a hemisphere of radius r. The refractive index of the glass is n. A point object O is at a distance u from the end of the rod. The image I due to refraction is at a distance v. which is twice the object distance u from the end of the rod. Which of the following is equal to u?

n

r

O

2r u

A

(n + 2)r n

B

(n + 2)r 2(n − 1)

C

2(n − 1)r n+2

D

2(n − 1)r n−2

v

I

19. The minimum distance between a real object and its real image formed by a convex lens is d. What is the distance of the object from the lens? A

d 4

B

d 3

C

d 2

D

3d 4

20. A beam of light which consists two different wavelength λı and λ2 (λı > λ2) is incident normally on a piece of diffraction grating. The second order line for λı and the third order line for λ2 overlap. What is the ratio of A 1.5

B 2.0

λ1 ? λ2

C 2.5

D 3.0

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21. Monochromatic light of wavelength λ in incident normally on a single slit as shown in the figure.

x P R Q

S In the direction of the first minimum, the path difference x between the rays PQ and RS is A

λ

B

4

λ 2

C

λ

D

3 λ 2

22. Nitrogen gas at a pressure of 1.01 × 10 5 Pa has a density of 2.5 kg m −3 . The mean square speed of the molecules is A 256 ms-1 B 318 ms-1 C 348 ms-1 D 384 ms-1 23 The density of oxygen at normal atmospheric pressure of 1.01 x 10 5 Pa is 1.40 kg m −3 . Find the mean kinetic energy of an oxygen molecule. ( The relative molecular mass is 32 ) A B C D

3.71 4.71 5.75 6.75

× 10 −23 J × 10 −27 J × 10 −21 J × 10 −23 J

24 In the thermodynamic process, the temperature of a quantity of an ideal gas decreases from 90 o C to 30 o C as 3 kJ of heat is removed from the gas and 2 kJ of work is done to the gas. Find the number of moles of the gas present. A 1.34 mol B 1.68 mol C 2.7 mol D 3.2 mol

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25 1650 J of heat is needed to raise the temperature of 5.0 moles of hydrogen gas under constant volume condition by 15 K. Assuming that hydrogen gas behaves like ideal gas, find the molar specific heat capacity at constant pressure for hydrogen gas. A 30.8 J mol −1 K −1 B 50.6 J mol −1 K −1 C 73.8 J mol −1 K −1 D 81.4 J mol −1 K −1 26. One end of a properly insulated copper rod of length 60 cm and cross-sectional area 6.0 cm 2 is maintained at steam point while the other end is placed in ice at 0 o C. Determine the mass of ice melted in 12 minutes if the rod is in steady condition. ( For copper k = 380 W m −1 K −1 : specific latent heat of fusion of ice = 333 kJ kg −1 ) A 0.04 kg B 0.08 kg C 2,48 kg D 3.56 kg 27. The circuit below includes an operational amplifier.

Given that R 1 = R 2 = R 3 = R 4 , which of the following expressions gives the magnitude of the output voltage V o ? A

V1 + V2 + V3

  R4  B ( V 1 + V 2 + V 3 )   R1 + R 2 + R 3  R  R1  R   + V 2  2  + V 3  4 C V 1   R4   R4   R3 D

 R + R2 + R3   ( V 1 + V 2 + V 3 )  1 R4  

  

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28. A point charge QB is moved round another positive point charge QA on a circular path of radius r. The work done on the charge QA in making one complete revolution is A.

QA QB (2r ) 4πεο

C.

QA QB 4πεο r 2

B.

(4π r )

QA QB 4πεο r 2

(2π r )

D. Zero

29. A circle of radius R is drawn in side a uniform electric field E as shown. VA, VB, VC and VD are respectively the potentials of points A, B, C and D at the periphery of the circle.

A•

E •

•

D

B

•

C

Which of the following best describe the relationships between VA, VB, VC and VD? B. VA= VC; VB < VD. D. VA < VC; VB = VD.

A. VA= VC; VB = VD. C. VA > VC; VB = VD.

30. Three charges lie along the x-axis. The positive charge Q1 =15 μC is at x = 2.0 m and the positive charge Q2 = 6.0μC is at the origin. Where must a negative charge Q3 be placed on the x-axis so that the resultant force acts on it is zero? A 0.68 m

B 0.78 m

C 9.88 m

D 0.98 m

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31. Two capacitors of capacitance 2 µF and 3 µF are joined in series and this combination is connected to a voltage source. The energy stored in the system is US. When the same capacitors are joined in parallel and then connected to the same voltage source the energy stored is UP. What is A. 2 : 3 C. 6 : 5

US ? UP

B. 3 : 2 D. 6: 25

32. What is the relationship between the drift velocity Vd of electron and the applied electric field E? A. Vd α E2 C. Vd α

B. Vd α E. 1 D. Vd α

E

E

33. The resistivity of iron is 1 × 10−7 Ω.m. The resistance of the iron wire is 1 Ω. If the diameter and length of the wire are both doubled, what is the new resistivity of the wire? A. 1 × 10−7 Ω.m. C. 4 × 10−7 Ω.m.

B. 2 × 10−7 Ω.m. D. 8 × 10−7 Ω.m.

34. The figure shows the current distribution in a part of an electrical circuit. Find the value of I? 2A 1A I 2A 3A

A. 1 A C. 1.5 A

B. 2 A D. 3 A

1A

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35, What is the equivalent resistance between point A and point B in the network as shown in the figure?

A

A. 2R C.

3 R 2

C 2R

2R

D

R

B

R 2 2 D. R 3 B.

36. A straight wire PQ carrying a constant current I is placed at right angles to a uniform magnetic field, as shown by the dotted line in the diagram.

The wire is then rotated through an angle θ about an axis perpendicular to the plane of the diagram. Which graph shows how the magnitude of the magnetic force F on the wire varies with θ in the range 0º to 90º?

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37. An electron beam enters a region in which there is an electric field perpendicular to the beam. A similar electron beam enters a magnetic field, also perpendicular to the beam direction. Does the magnitude of the force on the electrons depend on their speeds in their speeds in these two fields?

A B C D

Electric field no no yes yes

Magnetic field no yes no yes

38. A uniform magnetic field of flux density B passes normally through a plane 1 area A. In this plane lies a coil of eight turns of wire, each of area A . 4

What is the magnetic flux linkage for the coil? A

1 BA 4

B BA

C 2BA

D 8BA

39. The diagram shows a short coil would over the middle part of a long solenoid.

The solenoid current I is varied with time t as shown in the sketch graph. As a consequence, the flux density of the magnetic field due to the solenoid varies with time. The relation between B and I is B=μon I.

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Which graph shows how the e.m.f. E induced in the short coil varies with time?

D

40. There is a sinusoidal alternating current in a resistor. What is the mean power dissipated in the resistor? A B

1 2 1 2

(max imum current ) 2

C

(max imum power )

D

1 (max imum current ) 2 2 1 (max imum power ) 2

41. A sinusoidal supply of frequency 100 Hz and r.m.s. voltage 12V is connected to a 2.2 μF capacitor. What is the r.m.s. value of the current? A 0.42μA

B

5.5μA

C 17μA

D 26μA

42. Which of the following quantities of the incident light affect the maximum kinetic energy of the electrons ejected in the photoelectric effect experiment? A Speed

B Amplitude

C Frequency

D Intensity

43. An electron microscope has resolving power of about 100 times better than that of the optical microscope because A. electrons behave as particles B. the size of electrons is very small C. the electrons have much shorter wavelength D. the image observed in the electron microscope is monochrome.

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44. The diagram below shows the electronic transitions in an atom.

Which of the following spectral series is observed as a result of the transitions? A Increasing wavelength

B Imncreasing wavelength C Increasing wavelength D Increasing wavelength

45. X-rays can be diffracted by crystals but not by optical diffraction gratings because A. B. C. D.

X-rays have very high penetrating power. X-rays have very long wavelength. lines in the optical diffraction grating are too close to each other. wavelengths of X-rays are of the same order of magnitude as the crystalline atomic plane spacing.

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46. The figure below shows the paths of the ions of the isotopes of an element in a mass spectrometer 28 cm

The ratio of the masses of the three isotopes of the same charge is A C

2 : 4 : 28 18 : 20 : 24

B 11 : 12 : 14 D 31 : 32 : 36

47. The table below shows the count rate of a radioactive source at different times at a location. Time (hours)

Count rate (count per second)

10 30 90

Without source (Background radiation) 8 8 8

With source 48 18 8

Determine the half-life of the source based on the data given in the table A 5 hours

B 10 hours

C 12 hours

D 18 hours

48. .The rest mass of a 12 H deuteron atom corresponds to energy of 1876 MeV, the rest mass of a proton corresponds to 939 MeV and the rest mass of a neutron corresponds to 940 MeV. A deuteron can be fused to become a neutron if it

A emits a photon of gamma ray with energy 2 MeV B captures a photon of gamma ray with energy 2 MeV C emits a photon of gamma ray with energy 3 MeV D. captures a photon of gamma ray with energy 3 MeV

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49. In general, the fission of a heavy nuclear will produce two small nuclei, two or three neutrons, several β -particles and a little γ -radiation. It is always true that the product A B C D

have total rest mass that is greater than the original mass of the nucleus. have most of the kinetic energy originated from part of the loss in energy. move in exactly opposite directions have a ratio of neutron to proton that is too low to maintain stability.

50. Muon, an elementary particle with weak forces, is in the same category as the A proton

B electron

C Neutron

D

Pion

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Section A [40 marks] Answer all the questions in this section. 1.

A student suggests that the force F acting on a vertical wall due to a horizontal jet of l iquid st riking t he wall i s given by t he expression F = kρAv where k is a dimensionless constant, ρ, A and v represent the density of the liquid, the cross sectional ar ea of t he jet a nd sp eed o f t he jet r espectively. I s the ex pression dimensionally correct? [5 marks]

2.

(a) An object moves at constant speed in a circular path. (i)

Using Newton’s law of motion, explain why an external force is needed to apply to the object. [2 marks]

(ii)

Describe qualitatively the direction of the force.

[2 m arks]

(iii) Name the force. [1 mark]

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The figure bel ow sh ows a wheel of r adius 30 cm t hat i s brought t o r est uniformly f rom an a ngular velocity o f 2.0 r evolutions p er se cond. If t he belt that passes through the wheel is 25 cm,

Wheel

Belt

Calculate

4.

(a)

the number of revolutions completed.

[2 m arks]

(b)

The angular acceleration

(a)

Calculate the electric potential midway between two identical charges, +20 µC, placed 30 cm apart in vacuum. Take the value of εo = 8.9 × 10−12 F m−1. [2 marks]

[2 marks]

……………………………………………………………………………………… ………………………………………………………………………………………. (b) (i) Explain what is meant by an equipotential surface. ………………………………………………………………………………………. ………………………………………………………………………………………. [1 mark] 960/2 *This question paper is CONFIDENTIAL until the examination is over.

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Explain why a place anywhere in an electric field will be an equipotential surface. …………………………………………………………………………………………….. ……………………………………………………………………………………………... ……………………………………………………………………………………………. [2 marks]

5. Two welll-lagged u niform copper rods and well-lagged uniform iron rod, each of cross-section ar ea 6. 0 × 10 −5 m 2 and l ength 1 2 c m, are j oined end-to e nd as shown i n the figure below. The free ends are maintained at 2000 C and 00 C respectively.

2000 C

Copper

Iron

θ1

00 C

Copper

θ2

Given the thermal conductivity of copper is 380 W m -1 K 40 W m -1 K -1.

-1

and that of iron is

Calculate (i)

θ1 and θ 2

[ 4 marks]

(ii)

the rate of heat flow through the composite rod.

[2 marks]

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

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papercollection CONFIDENTIAL* -46. The di stance b etween t he pl ates o f a parallel capacitor is 5.0 mm and the area of each plate is 2.0 mm 2. The plates are in a vacuum. The potential difference of 1.0 × 104 mm is applied across the plates.

Find:

7.

(a) the capacitance,

[3 marks]

(b) the charge on each plate,

[2 marks]

The Bohr energy states En for the hydrogen atom is given by 13.6 E n = − 2 eV (n = 1, 2, 3...) n (i) Calculate the ionisation energy in joule for the hydrogen atom?

[3 marks] (ii) From the above equation, write the expression for the energy states En of helium ion 24 He + .

[2 marks] 960/2 *This question paper is CONFIDENTIAL until the examination is over.

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CONFIDENTIAL* -58. (a) Two similar coils A and B of core, as in

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insulated wire are wound on to a soft-iron

Figure 1.1 When the current I in coil A is switched on and then off, the variation with time t of the current is shown in figure 1.2. On figure 1.3, draw a graph to show the variation with time t of the e.m.f. E induced in coil B. [3 marks] I

O

t Figure 1.2

E

O

(b)

t

Figure 1.3

Explain why the transformer could not be used to step down the potential difference of a direct current supply. [2 marks]

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B

Answer any four questions in this section. 9.

Define work.

[1 mark]

Show that the units of work in terms of base units are given by kgm2s-2. [1 m ark] An object of mass 2.0 kg is at rest on a r ough horizontal plane. At the instant t = 0, a horizontal force F a cts on t he obj ect, c ausing t he object t o m ove at co nstant acceleration i n a s traight l ine. A t t = 1 0 s, the a pplied force i s removed. The object decelerates and comes to rest after moving for a t otal time of 15 s. The graph in figure below show how the velocity v of the object varies with time t. v/m s -1

10

0

5

10

15

t/s

(a) Determine the frictional force, which is assumed to be constant, that acts on the object between t = 0 s and t = 15 s. [2 marks] (b) Plot a graph to show how the applied force F varies with time t between t = 0 s and t = 15 s. on the graph show also the frictional force Ff. [6 marks] (c) Determine the total work done on the object (i)

by the applied force F between t = 0 s and t = 15 s.

(ii)

by the frictional force Ff between t = 0 s and t = 15 s.

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[3 marks] [2 marks]

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10. (a) The figure below shows two electrons separated by a distance of 3.0 x 10-10 m. Given that the gravitational constant = 6.67 x 10-11 N m2 kg-2, mass of electron = 9.11 x 10 -31kg, charge of electron = 1.60 x 10 -19 C and the permittivity of free space = 8.85 x 10 -12 F m -1.

Electron

Electron 3.0 x 10 -10 m

Calculate i..

the gravitational attractive force

[2 marks]

ii.

the electrostatic force between the two electrons.

[2 marks]

iii.

Why is it that the gravitational attractive force between two electrons can be neglected when compared to their resultant force? [2 marks]

(b)

i.

Write an equation for Newton’s universal gravitational law. State the meaning of the symbols used. [2 marks]

ii.

Given the radius of the Earth is 6400 km, the acceleration due to gravity at the surface of the Earth is 9.81 m s-2 and the gravitational constant G is 6.67 x 10-11 N m2 kg-2. Estimate a value for the mass of Earth. [2 marks]

iii.

Show that the gravitational field strength at a point of height h from GM the surface of the Earth is given by g = in which R is the 2 R +h radius of the Earth. [3 marks]

(

iv.

Find the escape velocity of the earth.

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

)

[2 marks]

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(a)

State three differences between progressive and stationary waves. [3 marks]

(b)

Explain the meaning of intensity of a progressive wave and state its SI unit.

[2 marks]

(c)

State whether stationary waves possess intensity. Explain your answer. [4 marks]

(d)

A circular progressive wave is produced on the surface of water from a point O by vibrating a dipper with constant amplitude. Explain why the amplitude of the wave decreases as the distance of the wavefront from O increases, by assuming that the absorption of energy by the medium is negligible. [4 marks]

(e)

At a distance r from O, the amplitude of the wavefront is A. Calculate the amplitude of the wavefront at a distance 2r from O. [2 marks]

(a)

Define magnetic flux density in terms of the force on a charge. Draw a diagram to show the quantities involved. [2 marks]

(b)

There are two situations in which a charged particle in a magnetic field does not experience a magnetic force. State these two situations. [2 marks] Figure shows a beam of electrons entering a magnetic field of magnetic flux density 8.4 mT. The electrons are traveling with velocity 3.4 × 107 m s-1 at right angles to the field.

(c)

Calculate, for the electrons in the field, the magnitude of (i) the force on an individual electron.

[2 marks]

(ii)

the acceleration of the electron.

[1 marks]

(iii)

calculate the radius of the path of the electrons within the magnetic field. [2 marks] Sketch the path traveled within and beyond the field. [2 marks]

(iv)

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c) Charged particles from the Sun, on approaching the Earth, may become trapped in the Earth’s magnetic field near the poles, as shown in Figure. This can cause the sky to glow. The phenomenon is called the aurora borealis.

Some of the charged particles travel in a circle of radius 50 km in a region where the magnetic flux density is 6.0 × 10-5 T. (i)

For a charged particle of charge to mass ratio e/m, deduce an expression for its speed v when traveling in a circle of radius r within a magnetic field of flux density B. [2 marks]

(ii)

Use your answer to (i) and the information about the path of the particles to show that the charged particles causing the aurora cannot be electrons. [2 marks]

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The graph shows the X-ray spectrum produced by a X-ray tube.

(a) (b)

Identify the two distinct features of the spectrum and explain how they are produced. [5 marks] Copy the graph above (with the labels) and sketch new graphs of the Xray spectrum produced when i. ii.

the current in the tube is increased the potential difference applied to the X-ray tube is decreased.

iii. (c)

the target metal is replaced with another element with higher atomic number. [6 marks] The inter-planar spacing of a crystal of NaCl is 0.282 nm. It is found that a first-order Bragg reflection of a monochromatic beam of X-rays occurs at an angle of 11o.

i. ii.

What is the wavelength of the X-rays? At what angle would a second-order reflection occur?

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[4 marks]

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(a)

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Explain what do you understand by the term (i) (ii) (iii)

(b)

13 6

mass defect activity of radioactive atom nuclear fusion

[3 marks]

C is bombarded with a proton which has kinetic energy of 2.00 MeV in

an experiment to produce 137 N . Use a quantitative approach to determine if this experiment will succeed? [4 marks] (c)

A research nuclear reactor of 20% efficiency can produce a maximum power of 1.0 MW. The nuclear fuel used is 235U , and the nuclear assumed to be represent by the nuclear fission reaction below U +

235 92

n →

1 0

148 57

La +

85 35

( )

Br + 3 01 n

(i)

State what is the role played by the neutrons produced in the above nuclear reaction [1 mark]

(ii)

Calculate the energy released by each of the the fission.

(iii)

Calculate number of 235U atoms used by the reactor in a period of 12 hours if the reactor is operating at maximum power [4 marks]

[ Mass of

U = 235.0439u ;

235

148 57

La = 47.9314u ;

85 35

U atom which undergoes [3 marks]

235

Br = 84.9156u ;

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1 0

n = 1.0097u ]

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ANSWER TRIAL EXAM PHYSICS STPM PAPER 1 2009 1. C 6. B 11. B 16. D 21. C 26. B 31. D 36. D 41. D 46. B

2. C 7. C 12. D 17. C 22. C 27. A 32. B 37. B 42. C 47. B

3. C 8. B 13. A 18. B 23. C 28. D 33. A 38. C 43 .C 48. D

4. A 9. A 14. D 19. C 24. A 29. B 34. A 39. C 44. D 49. B

5. B 10. D 15. D 20. A 25. A 30. B 35. B 40. D 45. D 50. B

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ANSWERS 1.

STRUCTURE

Let F = k ρm An vp MLT-2 = [ML-3]m [L2]n [LT-1]p (1m) = Mm L-3m+2n+p T-p Compare m = 1 -3m+2n+p = 1 P =2 Solving, we get m =1, n = 1, p = 2 and F = kρAv2

(1m)

(2m)

Hence, the expression F = kρAv suggested by the student is incorrect. ( 1 m ) 2. (a) According to the Newton’s first law of motion, an object at rest will continue to remain at rest, or if moving, will continue to move with constant velocity along a straight line, if no external forces act on the object. ( 1 mark ) An object moving i n a ci rcular p ath al ways change i ts di rection, so, an ex ternal f orce is needed to apply to the object. ( 1 mark )

3.

(b) The force is perpendicular to the velocity and always point towards the centre of the circle.

( 1 mark ) ( 1 mark )

(c) Centripetal force

( 1 mark )

b. ω 2 = ω 0 4.

25 = 13.3 2π × 0.30 + 2αθ ; 0 = 2.02 + 2 α (13.3); α = −0.5 revolution/sec 2

a. The number of revolutions completed =

(a) V =

2

20 × 10−6 4π(8.9 × 10−12 ) × (15 × 10−2 ) 6

= 2.38 × 10 V. (b)

1 mark

+

20 × 10−6 4π(8.9 × 10−12 ) × (15 × 10−2 )

Total marks for 1 (a): (2 marks)

(i) An equipotential surface is a surface over which all points are at the same electrical potential. Total marks for 1. b (i) : (1 mark) (ii) If there were any differences in electric potential over the surface of the metal, then its conduction electrons would move under the influence of the potential gradient. (1 mark) This electron movement would eventually reduce the potential differences to zero. (1 mark) Total marks for 1. b (ii) : (2 marks)

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5 (a) (i) Since the rod are well-lagged, the rate of heat flow is constant in each rod and is the same in the copper and the iron rods. dθ dQ Apply = − kA dx dt For the copper-iron pair

200 − θ1 = 0.105 ( θ1 − θ 2 ) 200 − θ1 = 0.105 θ1 − 0.105θ 2 200 = 1.105 θ1 − 0.105θ 2 ……………………………………..(1) For the iron-cooper pair on the right θ 2 = 0.105 ( θ1 − θ 2 ) 1.105θ 2 = 0.105 θ1 ……………………………………………..(1) Substitute copper × iron  0.105  200 = 1.105 θ1 - 0.105  θ1  …………………….(1)  1.105  θ1 = 181o C θ 2 = 17.2 o C ……………………………...(1)

Q  θ − θ2  = kA 1  ……………………………..(1) t  x  For the copper rod on the left

(ii) Rate of heat flow

Q  200 − 181  = 380 ( 6.0 × 10 −5 ) −2  t  12 × 10  = 3.61 J s −1 ……………………………………………….(1)

6.

(a) Capacitance of the parallel plate capacitor C=

=

εο A d

[1 mark]

8.85 × 10−12 × 2 5 × 10−3 −9

= 3.54 ×10

F

[1 mark]

F.

[1 mark]

(b) The charge on each plate. Q = CV −9 4 = (3.54 ×10 ) × (1 ×10 ) C

= 3.54 ×10

−5

C

[1 mark] [1 mark]

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7．.

The Bohr energy states En for the hydrogen atom is given by 13.6 ( n = 1,2,3……..) E n = − 2 eV n (i) Calculate the ionisation energy in joule for the hydrogen atom? [3 marks] 1 E − E 1 Ionisation energy = ∞ 0−−

=

13.6 1

1

= 13.6 eV

1

(ii) From the above equation, write the expression for the energy states En for helium ion 4 + [2 marks] 2 He . Z =2 4 × 13.6 n2 54.4 = − 2 eV n

1

En = −

8.

1

(a) I

O

t Figure 1.2

E

O

(b)

t

Figure 1.3

To step down voltage in the transformer by electromagnetic induction requires a change in flux linking the primary and secondary coil. These are not present in direct current supply.

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Work = force component in the direction of motion x displacement ( 1 mark ) Unit of work = Nm = (kgms-2)(m) = kgm2s-2 ( 1 mark ) (a) The applied force F is removed at t = 10 s. Hence, only frictional force Ff acts on the object during the time interval between t = 10 s and t = 15 s. Refering to the graph, the decerelation is a2 = gradient = -10/5 = -2ms-2 ( 1 mark ) 9.

then Ff = ma2 = 2 x -2 = -4 N ( 1 mark ) (b) Between t = 0 s and t = 5 s, the acceleration a1 is a1= gradient = 10/5 = 2ms-2 ( 1 mark ) then F – Ff = ma1 F–4 =2x2 ( 1 mark ) F = 8.0 N Between t = 5 s and t = 10 s, the acceleration is zero as velocity is constant. then F – Ff = ma = 0 ( 1 mark ) F = Ff = 4.0 N ( 1 mark ) Between t = 10 s and t = 15 s, the applied force has been removed, hence, F = 0 N.

Correct graph ( 1 mark ), include correct frictional force

( 1 mark )

(c)(i) Between t = 0 s and t = 5 s, Work done = F x disp. = 8 x ½(10)(5) = 200 J Between t = 5 s and t = 10 s, Work done = F x disp. = 4 x (10)(5) = 200 J Between t = 10 s and t = 15 s, F = 0 N Work done = F x disp. = 0 J Total work done = 200+200+0 = 400 J

( 1 mark ) ( 1 mark ) ( 1 mark )

(ii)Work done by Ff = Ff x disp. =- 4 x ½(10)(5 +15)

( 1 mark )

= -400 J

( 1 mark )

10. (a)

(

)(

Gm 2 6.67 × 10 −11 9.11 × 10 −31 i. Gravitational force F1 = 2 = 2 r 3.0 × 10 −10

ii.

Electrostatic force F2 =

)

2

(1.60 ×10 ) = 4π (8.85 ×10 )(3.0 ×10 ) −19 2

e2 4πε 0 r

(

)

2

−12

−10 2

= 6.15 × 10 −52 N

= 2.56 ×10−9 N

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iii.

F2 2.56 × 10 = = 4.16 × 10 42 . This means that the electrostatic force is F1 6.15 × 10 −52

(4.16 × 10 )times more than the gravitational force until the value of the gravitational 42

force can be neglected. GM 1 M 2 ; r2 F : gravitational attractive force between two objects, M1M2 : masses of the two objects G : gravitational constant r : separation of the two objects ii. : On the surface of the Earth, the gravitational force acting on an object of mass m equals its weight. GMm 6.67 × 10 −11 M = mg ; = 9.81; ∴ The mass of Earth M = 6.02 × 10 24 kg 3 2 R2 6400 × 10

(b)

i.

F=

(

(

) )

iii. The weight of an object at a height h from the surface of the Earth is mg. This value is the same as the gravitational attractive force between the object and the Earth. GM 1 GM mg = ∴ the gravitational field strength g = 2 (R + h ) ( R + h )2 iv.

v=

11.

(a)

2 gR =

2 × 9.81 × 6400 × 10 3 = 1.12 X 10 4

Stationary waves

Progressive waves

•

The profile of wave does not move

•

The profile of the waves move in the direction of propagation

•

No energy transferred along the wave

•

Energy transferred along the direction of wave propagation

•

Points in between two nodes are in the same phase.

•

Nearby points are not in the same phase.

•

Particles between successive nodes have different amplitudes

•

Neighbouring particles in the medium have the same amplitude of oscillation. Any three [3] (b) Intensity of a progressive wave is the power propagated per unit area, perpendicular to the direction of propagation.[1] P I = , where P = Rate of energy transferred and A = area of surface SI unit : Wm-2 [1] A (c) Stationary waves do not possess intensity. [1] Explanation: Stationary waves do not transfer energy. [1] The energy is restricted to a certain area. [1] Hence the rate of energy transferred, P is zero. P = 0, Intensity, I = 0. [1]

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(d) The intensity of a wave from a point source is inversely proportional to the distance from the source.  1 [1] Iα r Intensity of the wave decreases as the distance of the wavefront from O increases. As the distance of the wavefront from O increases, circumference of wavefront increases. [1] The same energy is distributed over a longer length. [1] Intensity is proportional to the square of the amplitude. I α a 2

[1]

Hence, the amplitude of the wave decreases as the distance of the wavefront from O increases. 1 r I α a2 1 a 2α r 2 a r = constant 2 2 a 2 r2 = a1 r1

(e) I α

a2

2

a=

A2 r = 2r A

[1]

[1]

2

12. (a) Definition : The magnetic flux density or magnetic field strength of a magnetic field is 1 tesla (T) if a charge of 1 coulomb moving with a velocity of 1 m s-1 at right angles to the direction of the magnetic field experiences a force of 1 newton. v

q

F

B

(b)

- the charged particle is stationary. - the charged particle is moving in a plane that is parallel to the magnetic field lines.

(c)

(i)

F = Bev = 8.4 ×10 −3 ×1.6 ×10 −19 × 3.4 ×10 7 = 4.6 × 10 −14 N

(ii)

F m 4.6 ×10 −14 = 9.11×10 −31 = 5.0 ×1016 m s −1

a=

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(iii)

mv 2 r (9.11× 10 −31 )(3.4 × 10 7 ) 2 = 4.6 × 10 −14 = 22.9 mm

F=

(iv)

Tangential to the curve

Region of magnetic field vertically down into the paper Electron beam

(d)

mv 2 mv 2 ==> Bev = r r

(i)

F=

(ii)

If they are electrons,

==> Be =

mv e == > v = Br   r m

 1.6 × 10 −19   v = (6.0 × 10 −5 )(50 × 10 3 ) −31   9.11 × 10  = 5.3 × 1011 m s −1 > speed of light. Therefore the charged particles causing the aurora cannot be electrons.

13. a)

The two distinct features are the continuous spectrum and the characteristic line spectrum. The continuous spectrum is produced by X-ray emitted as an electron decelerates when approaching the target metal. The incident electrons may penetrate an atom and collide with electrons in the K shell of the atom raising them to higher energy levels. The line spectrum is due to the radiation emitted when electrons from the excited state return to the lower energy levels.

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b)

(i)

(iii)

c)

(i)

(ii)

(ii)

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c)

i

ii

14.. (a) (i) Mass defect : The difference between the total mass of all free nucleons and the mass of the nucleus. (ii) Activity is the rate of nuclear disintegration or the number of nuclei decaying per unit time (iii) Nuclear fusion is the combination of lighter nuclei at very high temperature to produce a heavy nucleus with the release of a lot of energy

13 6

(b) 11 H +

C



13 7

N + 01 n

Change of mass in the reaction = (13.005739+1.008665)-(1.007825+ 13.003355) = 0.003224 u (2) This mass is needed to converted to energy of proton = 0.003224 x 931 MeV = 3.00 MeV (1) Given kinetic energy of proton is 2.00 MeV therefore this nuclear reaction will not succeed due the kinetic energy of the proton is less than that required for the change . (1) (c )

U + 01n 

235 92

148 57

La +

85 35

Br + 3 ( 01n )

(i) The neutrons produced ensure that the nuclear fission of U-235 will be continue in the nulear reactor

(1)

(ii) Mass defect ∆m = (235.0439+1.0087)-(147.9314+84.9156+3x1.0087) = 0.1795 u Energy released ; E = ∆m c 2 = (0.1795 x 1.66x 10 −27 )(3.00 x 10 8 ) 2 = 2.68 x 10 −11 J

(1) (1) (1)

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(iii) The energy produced by the reactor in 12 hours E =Pt = 10 6 x 12 x 60 x 60 = 4.32 x 1010 J

(1)

Use Formula efficiency = Output energy x 100% Input Energy Effeiciency of 20% = 4.32 x 1010 x 100% Nuclear energy Hence

Nuclear energy = 4.32 x 1010 x

100 20

=2.16 x 1011 J

(1)

(1)