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MINISTRY OF EDUCATION AND TRAINING

OFFICAL TEST
(The test has 05 pages)

NATIONAL HIGH SCHOOL EXAMINATION 2015

Subject: PHYSICS; group A and A1
Time: 90 minutes, not including delivering time
Code 138

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Registration number: ........................................................
Question 1: A spring-mass pendulum consisting of an object of mass m is in harmonic oscillation horizontally
with the equation: x = Acost. The potential origin is at the equilibrium position. The mechanical energy of the
pendulum is
A. mA2
B. 0.5mA2.
C. m2A2.
D. 0.5m2A2.
Question 2: An object is oscillating with the equation x = 5cos(t + 0.5π) (cm). The constant phase of
oscillation is
A. π.
B. 0.5π.
C. 0.25π.
D. 1.25π.
Question 3: An ideal LC oscillator consists of an inductor of inductance L and a capacitor of capacitance C. The
natural period of oscillation is
D. 2π LC .
C. LC .
B. 2πLC .

A. π LC .
Question 4: A point mass is oscillating with the equation x = 6cost (cm). The amplitude of oscillation is
A. 2 cm.
B. 6 cm.
C. 3 cm.
D. 12 cm.
Question 5: A spring-mass pendulum consists of a small object of mass m and a spring has constant spring k.
The angular frequency of the pendulum in harmonic oscillation is
m
k
m
k
A. 2π
.
B. 2π
.
C.
.
D.
.
k
m
k
m
Question 6: The root-mean-square voltage of civil single-phase electrical network in Vietnam is
A. 220 2 V.
B. 100 V.
C. 220 V.
D. 220 2 V.
Question 7: The opering principle of photoresistor is based on

A. photoluminescence.
B. outer photoelectric effect.
C. inner photoelectric effect.
D. thermoelectric effect.
Question 8: A mechanical wave of frequency f is propagating in an elastic string with the speed of propagation v
and the wavelength λ. The correct relation is
f
λ
A. v = λf.
B. v  .
C. v  .
D. v = 2πfλ.
λ
f
Question 9: A longitudinal wave is propagating in a medium, the direction of all elements in the medium
A. is horizontal direction.
B. is vertical direction.
C. coincides the direction of propagation.
D. is perpendicular to the direction of propagation.
Question 10: Electromagnetic wave is
A. longitudinal wave and enabled to propagate in vacuum.
B. transverse wave and enabled to propagate in vacuum.
C. longitudinal wave and not enabled to propagate in vacuum.
D. transverse wave and not enabled to propagate in vacuum.
Question 11: A mechanical wave propagates along Ox axis with the equation u = 20cos(20πt – πx) (cm) in
which t is in second. The frequency of this wave is
A. 15 Hz.
B. 10 Hz.
C. 5 Hz.
D. 20 Hz.

Question 12: Arcording to the quantum theory of light, which of the following statements below is correct?
A. The higher frequency of photon of monochromatic light is, the higher its energy is.
B. The energy of photon decreases gradually when the photon is gradually away from the source of light.
C. Photon exists in both stationary state and motion.
D. The energies of all types of photon are equal.
Question 13: The more stable nucleus is,
A. the greater nuclear binding energy per nucleon is.
B. the more number of photon is.
C. the more number of nucleon is.
D. the greater nuclear binding energy is.

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Question 14: The phase of the current intensity i = 2cos100πt (A) at time t is
A. 50πt.
B. 100πt.
C. 0.
D. 70πt.
Question 15: The equations of two oscillations are: x1 = 5cos(2πt + 0.75π) (cm) and x2 = 10cos(2πt + 0.5π) (cm).
The magnitude of the difference of phase of these oscillations is
A. 0.25π.
B. 1.25π.
C. 0.50π.
D. 0.75π.
Question 16: The work function of an electron emitted from a metal is 6.625x10-19 J, knowing that the Planck’s
constant is h = 6.625x10-34 Jxs, the speed of light is c = 3x108 m/s. The threshold wavelength of this metal is
A. 300 nm.
B. 350 nm.
C. 360 nm.

D. 260 nm.
Question 17: When it comes to infrared ray and ultraviolet ray, which of the following statements below is
correct?
A. The wavelength of infrared ray is greater than that of ultraviolet ray.
B. The infrared ray and the ultraviolet ray cause photoelectric effect for all metals.
C. An object heated emits ultraviolet ray and does not emit infrared ray.
D. The infrared ray and ultraviolet ray ionize strongly all gases.
Question 18: When it comes to emission spectrum, which of the following statements below is correct?
A. The emission spectrum of an element is a system of dark lines lying on the background of colors of
continuous spectrum.
B. The emission spectrum of an element is a system of single bright lines separated by dark spaces.
C. The emission spectrum of solid or liquid is emitted by heating.
D. In emission spectrum of hydrogen, four specific lines at the region of visible light are red line, orange line,
indigo line and violet line.
Question 19: A voltage u = U0cost (U0 is constant,  is variable) is placed across the circuit in series consisting
of a resistor R, a ideal inductor of inductance L and a capacitor of capacitance C. When  = 0, the circuit occurs
electric resonance. The angular frequency 0 is
2
1
A. 2 LC .
B.
.
C.
.
D. LC .
LC
LC
Question 20: In Truong Sa archipelago of Vietnam, to watch TV programs broadcasted from satellite, the local
people use antenna which receives directly the wave from the satellite, then the wave passes through the signal
processor and ultimately moves to screen. The electromagnetic wave which the antenna receive directly from the

satellite belongs to
A. medium-wave.
B. short-wave.
C. long-wave.
D. micro-wave.
Question 21: A 100 gram object is in oscillation with the equation x = 8cos10t (x in cm, t in second). The
maximum kinetic energy of the object equals
A. 32 mJ.
B. 64 mJ.
C. 16 mJ.
D. 128 mJ.
Question 22: Given that four radiations: α-ray, β+-ray, β--ray and γ-ray travel perpendicular to uniform electric
field. The radiation is not deviated from the initial direction is
A. α-ray.
B. β--ray.
C. β+-ray.
D. γ-ray.
Question 23: The nucleus 146 C and the nucleus 147 C are the same
A. charge.
B. number of nucleon. C. number of proton.
D. number of neutron.
10 4
Question 24: A voltage u = U0cos100πt (t in second) is placed across a
F-capacitor. The capacitive
π
reactance of the capacitor is
A. 150 Ω.
B. 200 Ω.
C. 50 Ω.
D. 100 Ω.

Question 25: A voltage u = 200 2 cos100πt (V) is placed across a pure 100 Ω-resistor. The power consumption
in the resistor is equal to
A. 800 W.
B. 200 W.
C. 300 W.
D. 400 W.
Question 26: A narrow monochromatic light beam is shone to a side of a glass prism in air. When have passed
through the prism, the light beam
A. is not deviated from the initial direction.
B. is changed in color.
C. is changed in frequency.
D. is not dispersed.
107
Question 27: Given that the nuclear masses: of 47 Ag is 106.8783u; of neutron is 1.0087u; of proton is 1.0073 u.
The mass defect of
A. 0.9868 u.

107
47

Ag is
B. 0.6986 u.

C. 0.6868 u.

Page 2/5 – Code 138

D. 0.9686 u.

Question 28: A 200 V alternating voltage is placed across the circuit consisting of an ideal inductor in series a
pure resistor. Assume that the root-mean-square voltage of the resistor is 100 V. The power factor of the circuit is
A. 0.8.
B. 0.7
C. 1.
D. 0.5.
Question 29: Which of the following types of luminescence below is photoluminescence?
A. The luminescence of a firefly.
B. The luminescence of an incandescent light bulb.
C. The luminescence of a common fluorescent lamp.
D. The luminescence of an LED (Light Emitting Diode).
Question 30: When it comes to X-ray, which of the following statements below is correct?
A. The penetrating of X-ray is not deeper than that of infrared ray.
B. The frequency of X-ray is lower than that of infrared ray.
C. The wavelength of X-ray is greater than that of visible light ray.
D. The physiologic function of X-ray is that: it destroys cells.
Question 31: A graph of the displacements of the point mass 1 (line 1) and the point
mass 2 (line 2) versus time as shown, the maximum speed of the point mass 2 is 4π cm/s.
No considering at t = 0, the time in which the two point masses at the fifth same
displacement is
A. 4.0 s.
B. 3.25 s.
C. 3.75 s.
D. 3.5 s.
Question 32: An atomic orbital of hydrogen is in stationary state. When a radiation of frequency f1 is illuminated
into this atomic orbital, they emit 3 radiations at most. When a radiation of frequency f 2 is illuminated into this
atomic orbital, they emit 10 radiations at most. Given that the energies relative to the stationary states of
E
f
hydrogen is defined by the formula E n   20 , where E 0 is a positive constant and n = 1, 2, 3,… The ratio 1

n
f2
equal
10
27
3
25
A.
.
B.
.
C.
.
D.
.
3
25
10
27
Question 33: Two ideal LC oscillators have the same maximum current intensity I0. The natural period of the
first LC circuit is T1 and that of the other circuit is T2 = 2T1. When the current intensities in the circuits are the
same magnitude and are greater than I0, the magnitudes of charge of the first and second circuit are q1 and q2,
q
respectively. The ratio 1 is
q2
A. 2.
B. 1.5.
C. 0.5.
D. 2.5.
2

Question 34: At the place of 9.8 m/s gravitational acceleration, a simple pendulum has a hanging rod of 1 m,
which is in harmonic oscillation with the angular amplitude of 1 rad. At the position in which the angular
displacement of 0.05 rad, the speed of the object of the pendulum is
A. 2.7 cm/s.
B. 27.1 cm/s.
C. 1.6 cm/s.
D. 15.7 cm/s.
Question 35: A standing wave is on an elastic string. On the string, the points in the oscillations of the same
amplitude A1 and A2 have adjacent equilibrium positions apart an equal distance d1 and d2, respectively. Assume
that A1 > A2 > 0. Which of the following expressions below is correct?
A. d1 = 0.5d2.
B. d1 = 4d2.
C. d1 = 0.25d2.
D. d1 = 2d2.
Question 36: At the position O in a factory, the fire alarm system (considering a point source) emit with a
constant sound power. From the outside, a device determining sound intensity level travels from M to O in 2
stages with the initial zero velocity and the magnitude of acceleration of 0.4 m/s2 until it stop at N (the gate of the
factory). Assume that NO = 10 m and sound intensity level (due to the emission of the system) at N is greater
than that at M 20 dB. Given that the transmission medium for sound is isotropic and it can not absorb sound. The
time interval that device travels from M to N is closest to which of the following values below?
A. 27 s.
B. 32 s.
C. 47 s.
D. 25 s.
Question 37: In a Young’s double-split interference experiment, the separation between the two splits is 0.5 mm,
the distance from the two splits to the screen is 2 m. A light source emits white light in the range of wavelength
from 380 nm to 760 nm. The point M in the screen is 2 cm apart from the central maximum. The longest
wavelength of all wavelengths creating bright fringe at M is
A. 417 nm.
B. 570 nm.

C. 714 nm.
D. 760 nm.

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Question 38: At water surface, two sources of coherent waves is placed at A and B 68 mm apart; which is in
harmonic oscillation with the same frequency, in phase and in the direction perpendicular to the water surface. In
the segment AB, two water elements oscillating with the maximum amplitude have the equilibrium positions
whose minimum distance is 10 mm. The point C is the equilibrium position of the element of the water surface
such that AC is perpendicular to BC. The water element at C is oscillating with the maximum amplitude. The
maximum distance AB is equal to
A. 37.6 mm.
B. 67.6 mm.
C. 64.0 mm.
D. 68.5 mm.
Question 39: A homogeneous spring which has a uniform cross-sectional area is cut into three springs whose
lengths are ℓ (cm), (ℓ - 10) (cm) và (ℓ - 20) (cm). Each of this springs is appied to a small object of mass m in
turn, there are three pendulums of natural periods: 2 s, 3 s and T, respectively; knowing that the constant
spring is inversely proportional to its natural length. The value of T is
A. 1.00 s.
B. 1.28 s.
C. 1.41 s.
D. 1.50 s.
Question 40: In a Young’s double-split interference experiment, the light source emits simultaneously two
monochromatic lights: the red light of wavelength of 686 nm and the blue light of wavelength λ in which
450nm < λ < 510 nm. On the screen, there are six blue bright fringes in the closest space between two bright
fringes which are same in color with the central maximum. How many red bright fringes are there in this space?
A. 4.
B. 7.

C. 5.
D. 6.
210
Question 41: The radioisotope 84 Po does alpha-radioactive decay into the stable isotope 206
82 Po with a half-life
of 138 days. Initially, there is a pure sample 210
84 Po . Until the time t, the total of the number formed nuclei of the
alpha and the Pb-206 is 14 times the remaining Po-210 nuclei. The value of t is
A. 552 days.
B. 414 days.
C. 828 days.
D. 276 days.
Question 42: A voltage u  U 2 cos ωt (U is constant, ω is variable) is placed in turn
across a circuit X and a circuit Y, in which X and Y are RLC in series circuits. In the figure,
PX and PY are represented the relation of the power consumption in X and in Y with respect
to ω, respectively. After that, the voltage u is placed across a circuit AB concluding X and
Y in series. The inductive reactance of the two ideal inductors in series (including ZL1 and
ZL2) is ZL = ZL1 + ZL2 and the capacitive reactance of the two ideal capacitors in series
(including ZC1 and ZC2) is ZC = ZC1 + ZC2. When ω = ω2, the power consumption of the
circuit AB has the value closest to which of the following values below?
A. 14 W.
B. 10 W.
C. 22 W.
D. 18 W.
Question 43: A voltage u = U0cos2πft (U0 is constant, f is variable) is placed across a circuit in series including an
ideal inductor of inductance L, a pure resistor R and a capacitor of capacitance C. When f = f1 = 25 2 Hz or
f = f2 = 75 Hz, the root-mean-square voltage of the capacitor has the same values U0. When f = f0, the root-meansquare voltage of the resistor is maximum. The value f0 is closest to which of the following values below?
A. 70 Hz.
B. 80 Hz.
C. 67 Hz.

D. 90 Hz.
Question 44: A horizontally tensing string OB with the two fixed ends is occurring
standing wave with a certain frequency f. Let M, N, P are three points on the string at
which the equilibrium positions apart from B 4 cm, 6 cm and 38 cm, respectively. The
figure decribes the shape of the string at the time t1 (line 1) and that at the time
11
t 2  t1 
(line 2). At the time t1, the displacement of element of the string at N is
12f
equal to that at M and the speed of element of the string at M is 60 cm/s. At the time t2,
the velocity of element of the string at P is
A. 20 3 cm/s.
B. 60 cm/s.
C. 20 3 cm/s.
D. –60 cm/s.
Question 45: Voltages u1, u2 and u3 which have the same root-mean-square voltage but the difference of frequency
are placed in turn across an RLC in series circuit, then the current intensites in the circuit are:
π
π
π



i1  I 2 cos 150πt   , i 2  I 2 cos  200πt   and i1  I cos 100πt   , respectively. Which of the
3
3
3




following statements below is correct?
A. the i2 is ahead of the u2.
B. the i3 is ahead of the u3.
C. the i1 is behind the u1.
D. the i1 and the i2 are in phase.

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Question 46: An alternating 20 V root-mean-square voltage of frequency of 50 Hz is placed
across a primary coil of an ideal transformer whose total number of turn of the primary and
the secondary is 2200 turns. The secondary is connected into a circuit AB as shown, in which
there are a constant resistor R, an ideal 0.2 H-inductor and a variable capacitor C. The
103
capacitance C is adjusted to C  2 (F), the ideal volmeter shows the maximum value
3π
103.9 V (approximately equal to 60 3 V). The number of turn of the secondary is
A. 400 turns.
B. 1650 turns.
C. 550 turns.
D. 1800 turns.
Question 47: A student determined the capacitance of a capacitor by placing a
voltage u = U0cosωt (U0 is constant, ω = 314 rad/s) across a circuit consisting of a
capacitor of capacitance C and a rheostat R in series. Given that
1
2
2
1
 2  2 2 2 2 in which the voltage U of the rheostat was measured by a
2

U
U0 U0ω C R
digital multimeter. Based on the experimental result as shown, the value of C
which student calculated is
A. 1.95x10-3 F.
B. 5.20x10-6 F.
C. 5.20x10-3 F.
D. 1.95x10-6 F.
Question 48: A 20 N/m light spring is suspended from a fixed end, the other end is attached to by a 100 g object
A, the object A is connected to a 100 g object B by a soft, thin, light, non-elastic and sufficiently long string. At
the equilibrium position of the system, the object B is vertically pulled down 20 cm then released it gently and it
moves with zero initial velocity. When the object B begins altering the direction, the object is slipped the string
suddenly. Resistance forces are negligible, knowing that g = 10 m/s 2. The time interval that the object B is
slipped until it falls at the dropped initial position is
A. 0.30 s.
B. 0.68 s.
C. 0.26 s.
D. 0.28 s.
7
Question 49 : A stationary nucleus 3 Li bombarded by proton whose kinetic energy is 5.5 MeV leads to the
nuclear reaction: p  73 Li  2α . Assume that the reaction has no gamma radiation, the two alpha nuclei have the
same kinetic energy and their directions of motion make a 1600 angle. Consider the nuclear mass in atomic unit
approximately equal to its mass number. The energy released is
A. 14.6 MeV.
B. 10.2 MeV.
C. 17.3 MeV.
D. 20.4 MeV.
Question 50: A voltage u = 400cos100πt (V) is placed across a circuit containing an ideal inductor of inductance
2
10 3

L, a resistor R and a variable capacitor C. When C  C1 
F or C  C1 , the powers of circuit have the same
8π
3
3
10
values. When C  C 2 
F or C  0.5C2 , the root-mean-square voltages of circuit have the same values. When
15π
an ideal alternating ammeter is connected to the two ends of the capacitor, the value the needle shows is
A. 2.8 A.
B. 1.4 A.
C. 2.0 A.
D. 1.0 A.

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