Download a-level physics paper i

MOCK EXAMINATION
A-LEVEL PHYSICS PAPER I
FORM: 7
Date:
Time:
NAME: ____________________
CLASS: 7 B
CLASS NO.: ______
STRUCTURED-TYPE QUESTIONS (50%, 120 marks)
i
There are 10 questions in this paper. Answer ALL questions.
ii
Write your answers in the spaces provided in this question-answer book. In calculations you should show
all the main steps in your working.
iii
Assume: speed of light in air = 3 ×108 m s-1
acceleration due to gravity = 10 m s-2
1.
(a)
In circuit A in the following figure, a “100 V, 30 W” light bulb is connected to a resistor of resistance
R and an a.c. of r.m.s. voltage 200 V and frequency 50 Hz. The light bulb is operated at normal
rating.
(i)
Find the r.m.s. current through the light bulb.
(ii) Find the resistance R.
(b)
(1 mark)
(1 mark)
In circuit B in the following figure, the resistor is replaced by a capacitor of capacitance C, and the
light bulb is again worked at normal rating.
(i)
Calculate the reactance of the capacitor.
F7EXM2103/CYT/P.1
(2 marks)
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(c)
(i)
Draw the phasor diagram below and label the phase difference between the voltage across the
bulb and the current passing through it. in both circuits.
Circuit A
(2 marks)
Circuit B
(ii) What is power factor in both cases ? How do they vary with the frequency of the power supply
?
(3 marks)
(iii) What happens to the brightness of the light bulb in circuit A and B when the frequency of the
a.c. source increases ?
(d)
(2 marks)
In terms of power dissipation, which circuit stated above is more suitable for lighting up the bulb ?
(1 mark)
F7EXM2103/CYT/P.2
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2.
In the X-ray tube shown in the above figure, the accelerating voltage is 100 kV are produced when the
tungsten target is bombarded by fast moving electrons. The X-ray spectrum is shown in the graph above.
Given h = 6.63  10-34 J s, e = 1.6  10-19 C and c = 3 x 108 m s-1.
(a)
Calculate the kinetic energy, in J, of the electrons before they hit the target.
(b)
Suppose there are 3.75  1016 electrons striking the target per second. What must be the power P
supply to X-ray tube ?
(c)
(1 mark)
A student says that this power is transferred to the electrons from the heat of the cathode. Do you
agree with the student ? Explain briefly.
(d)
(1 mark)
(2 marks)
Suppose the kinetic energy of an electron is completely transferred to a target atom, find the minimum
wavelength o of the X-ray photon.
F7EXM2103/CYT/P.3
(2 marks)
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(e)
Besides the condition stated in (d), name one additional condition for the emission of photons with
the shortest wavelength.
(f)
(i)
(1 mark)
Label the spectrum on the graph above, that is formed according to the deceleration of
fast-moving electrons interacting with the target metal.
(ii) Label the spectrum on the graph above, that is formed according to the electron transition from
high energy level to low energy level within the target metal.
(iii) Sketch on the graph above to show how the X-ray spectrum is changed by reducing the
accelerating voltage to one half.
(g)
3.
Give one application of X-ray.
(4 marks)
(1 mark)
The hospital treatment of internal tumors requires the uses of 2 mg of the radionuclide 60Co. Each decay
of it emits a particle of average energy 0.12 MeV followed by rays of total energy 2.5 MeV. A graph
of ln [Activity / count min-1] against time / year is shown in the following figure. Given that the Avogadro
number = 6.02  1023.
(a)
From the graph, determine the half-life of 60Co.
F7EXM2103/CYT/P.4
(2 marks)
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(b)
Calculate the number of nuclei in 2 mg of 60Co.
(c)
(i)
(d)
Find the initial activity of 60Co.
(1 mark)
(2 marks)
(ii) Find the initial power output from 2 mg 60Co.
(2 marks)
(iii) Deduce the power output from 2 mg 60Co after 21.2 year.
(2 marks)
Nowadays, a source technetium with a half-life of 6 hours is used instead of the source
Suggest TWO reasons why technetium is preferred.
F7EXM2103/CYT/P.5
60
Co.
(2 marks)
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(e)
Sometimes laser is used in the treatment of internal tumors instead. State TWO difference between
the laser and nuclear radiation in radioactive decay.
4.
(a)
(2 marks)
At a point 2 m from a small source of sound, the intensity is 4 10-7 W m-2. Find the rate of
emission of sound energy from the source. State your assumption(s) in the calculation.
(b)
(3 marks)
In the following figure, X and Y are two small loudspeakers having the same power as that found in
part (a). They vibrate in phase to emit sound of same frequency 170 Hz. Speed of sound in air =
340 m s-1.
2m
(i)
At point Z, the wave emitted from X has amplitude Ax, and the wave emitted from Y has
amplitude Ay. Find the ratio Ax / Ay.
F7EXM2103/CYT/P.6
(2 marks)
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(ii) Find the resultant intensity of sound at point Z.
(3 marks)
(iii) Now the loudspeaker Y is removed and a plane reflector is placed along the dotted line PQ.
Would you expect a louder or softer sound at Z ? Explain your answer.
(3 marks)
5.
In the figure above, a trolley of mass 1 kg traveling at a speed of 2 m s -1 towards a spring of force constant
10 N m-1 with a light pan at one end. Assume that the collision is elastic.
(a)
(i)
What physical quantities concerning the system are conserved ?
F7EXM2103/CYT/P.7
(2 marks)
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(ii) Find the time of contact between the pan and the trolley.
(2 marks)
(iii) Sketch a graph of force acting on the trolley with time during contact with the pan.
(2 marks)
(iv) Find the average force acting on the trolley during collision.
(2 marks)
(b)
The above procedure is repeated with one more identical spring connected in parallel as shown in the
figure above.
(i)
Find the time of contact between the pan and the trolley.
F7EXM2103/CYT/P.8
(2 marks)
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(ii) Without calculation, explain whether the average force acting on the trolley during collision is
greater than, equal to or smaller than the one in (a) (iv).
6.
(2 marks)
Given that G = 6.67  10-11 N m2 kg-2, earth-to-moon distance = 3.82  108 m, the mass of the earth =
5.98  1024 kg, the mass of the moon = 7.36  1022 kg, the radius of the earth = 6.37  106 m, and the
radius of the moon = 1.74  106 m.
(a)
Calculate the gravitational potential at
(i)
the surface of the earth (V1), and
(ii) the surface of the moon (V2).
(b)
(2 marks)
(2 marks)
It is given that at a certain distance ro from the centre of the earth, the gravitational potential is
maximum and equals to –1.29  106 J kg-1. What is the physical significance for the gravitational
field strength at this point ?
F7EXM2103/CYT/P.9
(2 marks)
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(c)
Draw a graph of gravitational potential with positions along the line joining the centers of the earth
and the moon.
(d)
(2 marks)
A spacecraft of mass 2 000 kg leaves the surface of the earth and travels to the surface of the moon.
(i)
What is the minimum energy it required on take-off to arrive at the moon ?
(2 marks)
(ii) With the minimum energy at take-off, find the speed of the spacecraft when it reaches the
moon’s surface.
(2 marks)
(iii) In fact, the spacecraft has to keep some fuel on board for landing on the moon safely. Explain
this.
7.
In a nuclear fusion process, a
(1 mark)
2
1H
nucleus and a 13 H nucleus fuse together to give a
4
2 He
nucleus and a
particle X.
(a)
(i)
Write down the equation to describe the above fusion process.
F7EXM2103/CYT/P.10
(1 mark)
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(ii) What is X ?
(1 mark)
(b)
Explain two functions of particle X in the thermal fission reactor.
(2 marks)
(c)
220
86 Rn
Given:
undergoes  decay to become
mass of a
mass of a
220
86 Rn
216
84 Po
1 u = 1.66  10
-27
216
84 Po .
nucleus = 219.9642 u
nucleus = 215.9558 u
kg
1 e = 1.6  10-19 C
(i)
Calculate the energy released in the  decay of a
(ii) Find the speed of the  particle.
F7EXM2103/CYT/P.11
220
86 Rn
into a
216
84 Po
nucleus in J.
(3 marks)
(3 marks)
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8.
yellow light
C
A
V
high resistance voltmeter
The experimental arrangement in the figure above is used to study photoelectric effect. When yellow light
is incident on an alkaline metal C, the high resistance voltmeter finally reads 1 V.
Given:
wavelength of yellow light = 580 nm
electronic charge = 1.6  10-19 C
planck constant = 6.63  10-34 J s
(a)
Calculate the energy of each incident photon.
(1 mark)
(b)
When yellow light is incident on the cathode, the voltmeter reading rises to 1 V and does not
increases further. Explain the phenomenon.
(2 marks)
(c)
What is meant by the ‘stopping potential’ of a metal ?
(1 mark)
(d)
Explain why the voltmeter reading remains unchanged when yellow light of greater intensity falls on
C.
F7EXM2103/CYT/P.12
(2 marks)
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(e)
The experiment is repeated with green light, blue light and violet light. The wavelengths of these
lights and the corresponding voltmeter readings are listed in the following table:
Colour of light
yellow
green
blue
580
520
470
 / nm
V/V
1
1.3
1.5
(i) Plot a graph of voltmeter reading V against frequency of light f.
violet
400
2
(4 marks)
(ii) Use the graph to find the work function of C.
(2 marks)
(iii) Draw the graphical result in the graph drawn in (i) when C is replaced by another metal of
greater work function.
(2 marks)
9.
load
frictionless piston
heater
In the figure above, a cylinder of volume 10-4 m3 fitted with a light and frictionless piston contains an ideal
gas at a pressure of 2  105 Pa and a temperature of 400 K. A load is placed on top of the piston.
Given:
molar gas constant = 8.31 J K-1 mol-1
Avogadro number = 6.02  1023
atmospheric pressure = 1.01  105 Pa
F7EXM2103/CYT/P.13
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(a)
(b)
(i)
Find the number of gas molecules inside the cylinder.
(3 marks)
(ii) Calculate the kinetic energy of each gas molecule.
(2 marks)
(iii) If area of piston is 10-3 m2, find the weight of the load.
(2 marks)
The gas is then heated at constant pressure to 600 K. Calculate
(i)
the new volume of the container.
(ii) the change in internal energy of the gas.
F7EXM2103/CYT/P.14
(2 marks)
(2 marks)
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10. A transistor of current gain  = 100 is connected with a 15 k base resistor and a 2.4 k load resistor as
shown. Assume that VBE = 0.7 V when the transistor is conducting and the minimum value for V CE is 0.2
V.
5V
15 k 
V
2.4 k 
RL
B
C
RB
E
Vout
0V
(a)
Find the ranges of voltmeter readings for the transistor to be
(i)
(b)
in the cut-off state,
(2 marks)
(ii) in the saturation state.
(2 marks)
Calculate the input voltage if the transistor is properly biased.
(2 marks)
The transistor is then properly biased as a linear voltage amplifier as shown.
F7EXM2103/CYT/P.15
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5V
2.4 k 
RL
B
C
15 k 
C1
RB
E
Vout
~
0V
(c)
What are the functions of capacitors C1 and C2 ?
(d)
Sketch the output waveform if the input signal is a sinusoidal a.c. at 50 Hz and with an amplitude of
(i)
(2 marks)
0.1 V,
(2 marks)
input signal
0.1 V
0
0.01
0.02
0.03
0.04
0.05
time / s
(ii) 0.3 V.
(2 marks)
input signal
0.3 V
0
0.01
0.02
0.03
0.04
0.05
time / s
- END OF PAPER SETTER CODE:
06
F7EXM2103/CYT/P.16
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Useful Formulae in Advanced Level Physics
v2
ω 2 r
r
A1.
a
A2.
a  ω 2 x
simple harmonic motion
A3.
L  I
angular momentum of a rigid body
A4.
T
A5.
1
E  I2
2
B1.
v
T
m
velocity of transverse wave motion in a stretched string
B2.
v
E

velocity of longitudinal wave motion in a solid
B3.
n  tan  P
B4.
d
B5.
d sin   n
B6.
f f(
B7.
10 log 10 (
C1.
F
C2.
V 
C3.
r 3 / T 2  constant
C4.
E
Q
40 r 2
electric field due to a point charge
C5.
V
Q
40 r
electric potential due to a point charge
C6.
E
C7.
C
C8.
Q Q 0 e t / RC
centripetal acceleration
dL
dt
torque on a rotating body
energy stored in a rotating body
refractive index and polarising angle
D
a
fringe width in double slit interference
diffraction grating equation
v uo
)
v u s
Doppler frequency
I2
)
I1
definition of the decibel
Gm1m2
r2
Newton’s law of gravitation
GM
r
gravitational potential
V
d
Kepler’s third law
electric field between parallel plates (numerically)
Q 0 A

V
d
capacitance of a parallel plate capacitor
t / RC
decay of charge with time when a capacitor discharges
C9.
Q Q 0 (1  e
C10.
1
E CV 2
2
energy stored in a capacitor
C11.
I  nAvQ
general current flow equation
C12.
R
C13.
F  BQv sin 
force on a moving charge in a magnetic field
C14.
F  BIl sin 
force on a moving conductor in a magnetic field
C15.
V
BI
nQt
Hall voltage
C16.
B
0 I
2r
magnetic field due to long straight wire
l
A
F7EXM2103/CYT/P.17
)
rise of charge with time when a capacitor is charged
resistance and resistivity
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C17.
B
 0 NI
l
magnetic field inside long solenoid
C18.
F
 0 I1 I 2
2r
force per unit length between long parallel straight current carrying
conductors
C19.
T  BANI sin 
torque on rectangular current carrying coil in uniform magnetic field
C20.
E  BAN sin t
simple generator e.m.f.
C21.
VS N S

VP N P
ratio of secondary voltage to primary voltage in a transformer
C22.
E   LdI / dt
e.m.f. induced in an inductor
C23.
1
E L I 2
2
energy stored in an inductor
C24.
X L  L
reactance of an inductor
C25.
XC 
1
C
reactance of a capacitor
C26.
P  IV cos 
C27.
Vout / Vin  
power in an a.c. circuit
RL
RB
voltage gain of transistor amplifier in the common emitter
configuration
C28.
V0  A0 (V  V )
C29.
A 
C30.
A1
D1.
pV  nRT  NkT
equation of state for an ideal gas
D2.
1
pV  Nmc 2
3
kinetic theory equation
D3.
Ek 
D4.
E
D5.
1
E  Fx
2
D6.
F 
D7.
E k/r
microscopic interpretation of Young modulus
D8.
1
p v 2 gh constant
2
Bernoulli’s equation
D9.
Q  U  W
first law of thermodynamics
D10.
En  
D11.
N  N 0 e  kt
D12.
t1 
2
Rf
gain of inverting amplifier
Ri
Rf
Ri
3RT 3
 kT
2N A 2
F
A
output voltage of op amp (open-loop)
x
L
dU
dr
13.6
eV
n2
ln 2
k
gain of non-inverting amplifier
molecular kinetic energy
macroscopic definition of Young modulus
energy stored in stretching
relationship between force and potential energy
energy level equation for hydrogen atom
law of radioactive decay
half-life and decay constant
D13.
1
2
mv m hv 
2
Einstein’s photoelectric equation
D14.
E  mc 2
mass-energy relationship
F7EXM2103/CYT/P.18
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