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JURONG JUNIOR COLLEGE
Preliminary Examination 2009
Name: _____________________________
Class: 08___________
9745/03
PHYSICS
Higher 2
Paper 3
2 Sep 2009
2 hours
Candidates answer on the Question Paper.
No Additional Materials are required.
READ THESE INSTRUCTIONS FIRST
For
Examiner’s Use
Do not open this booklet until you are told to do so.
Write your name and class in the spaces provided at the top of this
page.
Write in dark blue or black pen.
You may use a soft pencil for any diagrams, graphs or rough working.
Do not use highlighters, glue or correction fluid.
There are two sections in this paper. Section A has four questions.
Section B has three questions.
1
/10
2
/10
3
/12
4
/8
/20
Section A
Answer all questions.
/20
Section B
Answer any two questions.
You are advised to spend about one hour on each section.
At the end of the examination, fasten all your work securely together.
Total
/80
The number of marks is given in brackets [ ] at the end of each
question or part question.
(This question paper consists of 18 printed pages)
Preliminary Examination 2009
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2
Data
=
3.00  108 m s-1
speed of light in free space,
c
permeability of free space,
o = 4  107 H m1
permittivity of free space,
o = 8.85  1012 F m1 = (1/(36))  109 F m1
elementary charge,
e
=
1.60  1019 C
the Planck constant,
h
=
6.63  1034 J s
unified atomic mass constant,
u
=
1.66  1027 kg
rest mass of electron,
me =
9.11  1031 kg
rest mass of proton,
mp =
1.67  1027 kg
molar gas constant,
R =
8.31 J K1 mol1
the Avogadro constant,
NA =
6.02  1023 mol1
the Boltzmann constant,
k
1.38  1023 J K1
gravitational constant,
G =
6.67  1011 N m2 kg2
acceleration of free fall,
g
=
9.81 m s2
s
=
ut +
=
Formulae
uniformly accelerated motion,
1
at 2
2
v2 =
u2 + 2as
work done on/by a gas,
W =
p V
hydrostatic pressure,
p
=
gh
gravitational potential,

=

displacement of particle in s.h.m.,
x
=
xo sin t
velocity of particle in s.h.m.,
v
=
vo cos t
v
=
  ( xo2  x 2 )
resistors in series,
R =
resistors in parallel,
1/R =
Gm
r
R1 + R2 + . . .
1/R1 + 1/R2 + . . .
Q
electric potential,
V =
4 εo r
alternating current / voltage,
x
=
xo sin t
transmission coefficient,
T
=
exp(-2kd)
where k
=
radioactive decay,
x
=
decay constant,

=
82 m(U  E )
h2
xo exp(t)
0.693
t1
2
Preliminary Examination 2009
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3
Section A
Answer all the questions in the spaces provided.
1
(a)
State two differences between a systematic error and a random error.
(b)
The time taken for a simple pendulum to complete one oscillation may be
determined by using a stopwatch as shown in Fig.1.1.
[2]
Fig.1.1
Suggest one example of a systematic error which could occur in the experiment.
[1]
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(c)
The string of the pendulum bob in (b) was cut and the bob flies off into a
parabolic path at an angle of 15o to the horizontal platform at a speed of
2.5 m s-1 at 0.125 m above the ground as shown in Fig.1.2.
2.5 m s-1
15o
0.125 m
Fig.1.2
On Fig.1.3, the line OX represents the velocity of the pendulum bob at the instant
the string is cut.
2.5 m s-1
X
15o
O
Fig.1.3
(i)
Explain why OX represents the velocity of the bob and not its speed.
[1]
(ii)
Explain why the bob enters a parabolic path.
[1]
(iii) Calculate the maximum height reached by the bob above the ground.
Preliminary Examination 2009
[2]
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(iv) Calculate the time taken for the bob to hit the ground.
(v)
2
[2]
Calculate the horizontal displacement of the bob when it hits the ground
after the string is cut.
[1]
(a)
State the first law of thermodynamics.
[2]
(b)
Explain what is meant by the internal energy of a system.
[1]
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(c)
A fixed mass of an ideal gas is subjected to various changes of pressure, volume
and temperature through cycle ABCDA. The states A, B, C, and D of the gas are
shown in Fig.2.1 below.
Pressure / 105 Pa
2.0
0.5
0.5
1.0
State
A
B
C
D
Volume / 10-2 m3
1.5
6.0
2.0
1.5
Fig.2.1
The changes are shown in Fig.2.2 below.
p / 105 Pa
A
2.0
1.0
D
B
0.5
0
C
1.5
V / 10-2 m3
2.0
6.0
Fig.2.2
(i)
Fig.2.3 below gives quantitative data for some of these changes. Fill in the
blanks in Fig.2.3.
[4]
State
change
Process
Work done
on gas / kJ
A to B
Isothermal
4.16
B to C
Isobaric
C to D
Adiabatic
D to A
Isochoric
Heating
of gas / kJ
Change in
internal energy / kJ
5.63
0.36
0.36
Fig.2.3
(ii)
This is a process in a cylinder of a diesel engine. The cycle is repeated 10
times per second. Calculate the power output of this engine.
[2]
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(iii) Calculate the efficiency  of this engine where  is defined as
work output
=
heat input
3
(a)
[1]
Explain why the potential difference across the terminals of a normal battery is
always lower than its e.m.f when it is connected to a circuit.
State the condition under which the potential difference across a normal battery’s
terminals equal to its e.m.f.
[2]
(b)
Fig.3.1 shows a uniform wire XY of length 150.0 cm and resistance 4.5 Ω
connected in series with a cell Z of e.m.f. 3.0 V with internal resistance 0.5 Ω.
Z
0.5 Ω
3.0 V
X
Y
Fig.3.1
(i)
Calculate the potential difference between X and Y.
Preliminary Examination 2009
[2]
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Another circuit consisting of a cell W in series with 1.0 Ω and 2.0 Ω resistors is
connected to positions X and P which are 80.0 cm apart. These are illustrated in
Fig.3.2.
Z
0.5 Ω
3.0 V
80.0 cm
X
P
Y
G
1.0 Ω
2.0 Ω
F
E
A
W
Fig.3.2
(ii)
If the galvanometer registers a null deflection at position P, what is the
reading shown on the ammeter?
(iii) Calculate the power loss in cell Z.
[2]
[2]
(iv) Wire XY is replaced with another wire of the same material and length but
with a smaller cross-sectional area.
State and explain the changes (if any) in
1.
the balance length,
Preliminary Examination 2009
[2]
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2.
4
and the final ammeter reading at balance.
[2]
Strontium-90 decays with the emission of a -particle to form Yttrium-90. The decay
constant of Strontium-90 is 0.025 year-1.
(a)
Define decay constant.
(b)
At the time of purchase of a Strontium-90 source, the activity is 3.7  106 Bq.
[2]
(i)
Calculate, for this sample of strontium, the initial number of nuclei.
[3]
(ii)
Determine the activity of the sample 5.0 years after purchase.
[3]
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Section B
Answer two questions from this section. Each question carries 20 marks.
5
(a)
(i)
Define gravitational field strength at a point.
[1]
(ii)
Define gravitational potential at a point.
[1]
(iii) State the relationship between gravitational field strength g and gravitational
potential .
[1]
(iv) The equation for the gravitational potential in the field of a point mass is
GM
. Explain the negative sign in the equation.

r
(b)
(i)
[2]
Derive an expression for the gravitational field strength g at the surface of
the Earth. Express your answer in terms of the universal gravitational
constant G, the mass of the Earth ME and the radius of the Earth RE. State
two assumptions you make.
[4]
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(ii)
(c)
A common equation for the gravitational potential energy of an object above
the surface of the Earth is U  mgh . Suggest a reason why this equation
should not be applied when h is more than several kilometres.
[1]
A space vehicle of mass 500 kg moves in a circular orbit at a height of 1000 km
above the surface of the Earth. Given that the mass of Earth is 6.0 × 1024 kg and
radius of Earth is 6400 km, determine
(i)
gravitational potential energy U of the space vehicle
[2]
(ii)
linear speed v of the space vehicle
[3]
(iii) period T of the orbit of the space vehicle
[2]
(iv) The engine of the space vehicle provides energy for it to reach an infinite
distance from the Earth. Determine the minimum energy delivered by the
engine.
[3]
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6
(a)
(i)
Define magnetic flux density.
(ii)
Indicate on Fig.6.1 showing the directions of the other physical quantities
involved, in relation to the magnetic flux density B.
[1]
[2]
B
Fig.6.1
(b)
State the laws of electromagnetic induction.
Preliminary Examination 2009
[2]
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(c)
In an experiment, an electron travelling with a speed 2.3  107 m s-1 enters a
magnetic field of uniform flux density 0.40 T, in a direction at right angles to the
field as shown in Fig.6.2. The magnetic field is directed into the page.
B
speed = 2.3  107 m s-1
e
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Fig.6.2
(i)
Calculate the radius of the path of the electron in the field.
(ii)
The electron enters the magnetic field normal to the left edge of the field, and
exits normally from the same edge.
[2]
1.
Draw the path of the electron in the magnetic field.
2.
Calculate the duration of time for the electron to stay in the magnetic
field.
[2]
Preliminary Examination 2009
[1]
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(d)
Fig.6.3 shows the position of a wire in a magnetic field where the magnetic flux
density B is 0.40 T, directed to the right.

B
wire with current out of plane of paper
Fig.6.3
The wire, which is of length 0.12 m, carries a current of 3.0 A out of the plane of
the paper.
(i)
Draw a diagram to show the shape and direction of the magnetic field due to
the current in the wire.
[2]
(ii)
State the direction of the force acting on the wire.
(iii) Calculate the force acting on the wire.
Preliminary Examination 2009
[1]
[2]
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(e)
Fig.6.3 shows part of an electric motor. When the current in the wire is switched
off, the motor acts as an electrical generator.
(i)
(ii)
With the current switched off, the wire is moved to cut the magnetic flux
perpendicularly. Calculate the speed of the wire required to give an
instantaneous e.m.f. of 0.24 V.
[2]
The resistance of the wire is 0.15 . When the current in the wire is switched
on again, the wire moves with the speed as in (e)(i). This 3.0 A current in the
moving wire is supplied by a source. Calculate the e.m.f. of this source,
whose internal resistance is negligible.
[3]
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7
(a)
(b)
(i)
State what is meant by the photoelectric effect.
[1]
(ii)
List three experimental observations associated with this photoelectric
effect.
[3]
A lamp emitting light of wavelength 590 nm, is placed above a metal surface
which contains atoms of radius 2.0  1010 m. Each electron in the metal requires a
minimum energy of 4.0  1019 J before it can be emitted from the metal surface,
and it may be assumed that the electron can collect energy from a circular area
which has a radius equal to that of the atom. The lamp provides energy at a rate
of 0.50 W m-2 at the metal surface.
(i)
Estimate, on the basis of wave theory, the time required for an electron to
collect sufficient energy for it to be emitted from the metal.
[3]
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(ii)
(c)
Calculate the energy of the light photon and comment on your answer to
(b)(i).
[2]
Fig. 7 illustrates some of the electron energy levels in an isolated atom of lithium.
The energies of the levels are given in electron-volts (eV).
0
-0.67 eV
-0.94 eV
-1.43 eV
A
B
-2.49 eV
C D
-5.73 eV
-8.68 eV
Fig. 7
(i)
An electron of a lithium atom is in the lowest energy level shown. How much
energy is required to remove this electron from the atom?
[1]
(ii)
1.
Which of the transitions A, B, C or D will lead to emission of radiation
of the shortest wavelength?
[1]
2.
Calculate the wavelength of this radiation.
3.
State the region of the electromagnetic spectrum which this radiation
lies.
[1]
Preliminary Examination 2009
[2]
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(iii) Sketch in the diagram below the appearance of the spectrum which the four
transitions A, B, C and D produce. Label each line of the spectrum with their
corresponding letter.
[2]
Increasing frequency
(iv) The work function of lithium differs from the energy required to remove the
outer electron from an isolated lithium atom. Suggest why it is so.
[2]
(v)
The energy level at -5.73 eV is a metastable state that has a lifetime of
10-5 s. What is the uncertainty of the energy of this energy state?
[2]
End-of-Paper
Preliminary Examination 2009
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