2015 H2 Prelim P1 - jjphysics.pbworks.comjjphysics.pbworks.com/w/file/fetch/103030141/2015... · ©JJC 2015 9646/JC2 Prelim Exam P1/2015 [Turn Over 2 Data speed of light in free space,

©JJC 2015 9646/JC2 Prelim Exam P1/2015 [Turn Over

JURONG JUNIOR COLLEGE JC2 Preliminary Examination 2015

Name Class 15S

PHYSICS Higher 2

Multiple Choice

Additional Materials: Multiple Choice Answer Sheet Soft clean eraser Soft pencil (type B or HB is recommended)

9646/1

18 September 2015

1 hour 15 min

READ THESE INSTRUCTIONS FIRST 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 soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name, class and index number on the Answer Sheet in the spaces provided. There are forty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet.

(This question paper consists of 23 printed pages)


2

Data speed of light in free space, c = 3.00 × 108 m s−1 permeability of free space, μo = 4π × 10−7 H m−1 permittivity of free space, εo = 8.85 × 10−12 F m−1 = (1/(36π)) × 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 Formulae uniformly accelerated motion, s = ut + 1

2 at2

v2 = u2 + 2as work done on/by a gas, W = p ΔV hydrostatic pressure, p = ρgh gravitational potential,

φ = −Gm

r

displacement of particle in s.h.m., x = xo sin ωt velocity of particle in s.h.m., v = vo cos ωt v = 2 2( )ox xω± −

mean kinetic energy of a molecule of an ideal gas E = 3

2 kT

resistors in series, R = R1 + R2 + . . .resistors in parallel, 1/R = 1/R1 + 1/R2 + . . .

electric potential, V = o

Qε rπ4

alternating current / voltage, x = xo sin ωt transmission coefficient, T ∝ exp(−2kd)

where k = 2

2

8 ( )m U Eh

π −

radioactive decay x = xo exp(-λt) decay constant

λ = 1/2

0.693t


3

1 Four students A to D were measuring the potential difference across a piezo-electric material. Each student obtained 5 sets of data for the potential difference.

If the actual potential difference is 1.65 × 10−2 V, which student’s measurement was accurate but not precise?

Potential difference / 10−2 V Mean / 10-2 V

A 1.61 1.65 1.65 1.58 1.61 1.62

B 1.69 1.70 1.69 1.70 1.69 1.69

C 1.66 1.68 1.63 1.64 1.65 1.65

D 1.65 1.64 1.65 1.65 1.66 1.65

2 A boat changes its velocity from 8 m s-1 due north to 6 m s-1 due east.

What is its change in velocity?

A 2 m s-1 at a direction of 37° east of north

B 2 m s-1 at a direction of 53° east of north

C 10 m s-1 at a direction of 37° east of south

D 10 m s-1 at a direction of 53° west of south

3 A marble rolls off the edge of a horizontal table with a speed of 2.0 m s-1. The edge of the table is 1.2 m above the floor.

What is the horizontal distance the marble is away from the edge of the table when it hits the floor?

A 0.49 m B 0.99 m C 1.9 m D 2.3 m


4

4 A wire W, initially of length L, is fixed at one end and pulled by a force F at the other end. The wire extends by x.

Three wires, all identical with wire W, are connected as shown to form a composite wire.

The composite wire is fixed at one end and pulled by force 2F at its other end.

What is the total extension of the composite wire?

A 32

x B 2x C 8

3x

D 3x

5 A small block of wood, of density 400 kg m−3, is held fully submerged in water. What is the initial acceleration of the block towards the surface when the block is released?

(Take the density of water to be 1000 kg m3.)

A 1.5 m s-2 B 9.8 m s-2 C 15 m s-2 D 25 m s-2

6 When a 1000 kg car and a 10000 kg truck collide head-on, why is the passenger on the car more likely to experience a bigger force by the seat belt?

A The car experiences a bigger force than the truck.

B The passenger on the car experiences a larger impulse.

C The car undergoes a larger change of velocity than the truck.

D The force on the car is the same as the truck.


5

7 A student plotted a time-force graph as shown below.

Which of the following correctly show how change in velocity can be determined between time t = 0 s to t1?

A ×Gradient of the graph m

B

Area Am

C AreaBm

D ×AreaB m

8 A man intends to position a box by giving a push and letting go. He misjudges his push and the box goes only one-third of the way to the intended position.

If the initial speed of the box after the push is vo and the resistive force acting on the box is constant, what should the initial speed of the box be for it to slide to the intended position?

A 2 ov

B 3 ov

C 6 ov

D 3 ov


6

9 A car of mass m is accelerated horizontally from rest to a speed v by a constant force F. How much work is done on the car during this acceleration?

A 12

Fv

B Fv

C mv2

D 212

mv

10 The diagram below represents 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 centre of gravity is at G.

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

A B

C D

G

R

mg

R

mg

2mvr

2mvr

R

mg

R

mg

f


7

11 A simple pendulum is released from rest at A. What is the tension in the string when the pendulum is at position B (where the string is vertical), given that the mass of the bob is m and the length of the pendulum is L?

A 0.87 mg

B 1.0 mg

C 1.3 mg

D 2.0 mg

12 The moon orbits the Earth once every 27.3 days, with a mean orbital radius of R. The

period of an Earth satellite with an orbital radius of 30R is

A 0.17 hours

B 4.0 hours

C 68 hours

D 260 hours


8

13 P is a planet with centre O, as shown. X and M are two points of equal gravitational potential. Y and N are two other points of equal gravitational potential.

Which of the following statement(s) is/are incorrect?

I The work done by an external agent to move a mass from Y to X is negative.

II The work done by the gravitational field to move a mass from X to N is the same as that needed to move the same mass from M to N.

III The gravitational potential at X is smaller than the gravitational potential at Y.

IV =

gravitational potential at X distance OXgravitational potential at Y distance OY

A I, II

B II, III

C III, IV

D IV only

14 Which statement describes the electric potential difference between two points in a wire?

A The force required to move a unit positive charge between the two points.

B The ratio of the energy dissipated to the current flowing between the two points.

C The ratio of the power dissipated to the electric charge flow between the two points.

D The ratio of the power dissipated to the current flowing between the two points.


9

15 Two wires made of the same material and length are connected in parallel to the same voltage supply. Wire P has a diameter of 2 mm. Wire Q has a diameter of 1 mm.

What is the ratio current in Pcurrent in Q

?

A 14 B 1

2 C 2 D 4

16 In the circuit shown below, ammeter 1 and ammeter 2 have negligible resistance. The source has internal resistance 0.5 Ω and ammeter 1 reads 6 A.

Determine the reading of ammeter 2.

A 1.0 A B 2.7 A C 3.3 A D 5.0 A

17 A potentiometer consists of a 1.00 m long resistance wire XY in series with a battery of e.m.f. E1 9.00 V and internal resistance r 1.42 Ω. The resistance of wire XY is 8.30 Ω.

Determine the e.m.f. E2 if the balance length l is found to be 0.745 m.

A 0.636 V B 2.72 V C 5.73 V D 9.00 V


10

18 A fixed mass of ideal gas undergoes cyclical changes in pressure and volume as shown in the diagram below.

Which row of the table correctly describes the net work done on the gas and the heat supplied to the gas for one cycle?

Net work done on the gas Heat supplied to the gas

A Zero Negative

B Positive Negative

C Positive Positive

D Negative Positive

19 A fixed mass of an ideal gas absorbs 1000 J of heat and expands under a constant external pressure from an initial volume of 20 cm3 to a final volume of 50 cm3. The increase in the internal energy of the gas is 400 J.

Determine the constant external pressure.

A 13 MPa B 20 MPa C 33 MPa D 53 MPa


11

20 A mass hanging from a spring suspended from the ceiling is pulled down and released. The mass then oscillates vertically with simple harmonic motion of period T. The graph shows how its distance from the ceiling varies with time t.

What can be deduced from this graph?

A The amplitude of the oscillation is 70 cm.

B The kinetic energy is a maximum at t = T2

.

C The restoring force on the mass increases between t = 0 and t = T4

.

D The speed is a maximum at t = T4

.


12

21 The figure below shows two simple pendulums X and Y having the same lengths and same bob sizes and a simple pendulum Z whose length can be varied. (The density of polystyrene is less than the density of copper.)

The pendulum X and pendulum Y will oscillate after the pendulum Z is set into oscillations in a plane parallel to the wall.

Which of the graphs below shows the variation of the amplitude a for the pendulum X and pendulum Y with frequency f of the pendulum Z when the length of pendulum Z is varied?

A

B

C

D

0 f

a

Y

X

0 f

a

X

Y

f

a Y

X

Y X

a

f

Y


13

22 A sound wave of frequency 3600 Hz propagates from left to right through a gas. The diagram below shows the positions of some gas molecules at a particular instant of time.

The distance between particles P and Q is 0.500 m.

Which one of the following statements is true?

A The gas is not dry air at room temperature.

B The speed of the gas is 1800 m s-1.

C The pressure at P is always below atmospheric pressure.

D The sound wave is stationary.

23 An air column open at one end and closed at the other end is at resonance.

Which one of the following statements is always true?

A There is an odd number of nodes.

B There is an even number of nodes.

C The total number of nodes and antinodes is an odd number.

D The total number of nodes and antinodes is an even number.

24 In a Young’s double slit experiment, the intensity at the centre of the fringe pattern is I. If one of the two identical slits is now closed, the intensity at the centre of the pattern is

A I

B

2I

C 2I

D 4I


14

25 The arrows on the diagrams represent the movement of the air molecules in a pipe in which a stationary longitudinal wave has been set up. The length of each arrow represents the amplitude of the motion, and the arrow head shows the direction of motion at a particular instant.

Which of the following diagrams shows a possible stationary wave that could be set up in the pipe?

A II only

B III only

C II and IV

D I, II and IV

26 An electron travelling at constant speed enters a uniform electric field at right angles to the field. While the electron is in the field it accelerates in a direction which is in the

A same direction as the electric field.

B opposite direction to the electric field.

C same direction as the motion of the electron.

D opposite direction to the motion of the electron.


15

27 A +5.0 C point charge is initially stationary at a point P in a uniform electric field of strength 4.0 Vm−1. It is then moved 2.0 m parallel to the field and 3.5 m perpendicular to the field to a point Q as shown in the diagram below.

What is the work done by the electric field?

A −70 J

B −40 J

C 40 J

D 70 J

28 An electron is moving in air at right angles to a uniform magnetic field. The diagram below shows the path of the electron.

Which one of the following correctly gives the speed of the electron and the direction of the magnetic field?

Speed Direction of magnetic field

A decreasing into plane of paper

B increasing out of plane of paper

C increasing into plane of paper

D decreasing out of plane of paper


16

29 Three concentric coils X, Y and Z that are equally spaced apart, carry the same current in the directions as shown in the diagram.

Which of the following statement on coil X is correct?

A The directions of the forces acting on X are outwards, away from the centre of X.

B The directions of the forces acting on X are inwards, towards the centre of X.

C Coil X experiences forces that cause it to start rotating.

D Coil X experiences forces perpendicular to the plane of X, into the diagram.


17

30 A circuit containing a circular loop of wire connected to a low power light bulb is positioned around a solenoid connected to a sinusoidal AC source and a diode as shown in the diagram below.

Which of the following statements is true?

A The light bulb does not light up at all because the diode prevents current from flowing and thus producing any magnetic flux in the solenoid.

B The light bulb does not light up at all because the magnetic flux linkage through the loop does not reverse its direction.

C The light bulb lights up because the magnetic flux linkage through the loop reverses its direction every cycle.

D The light bulb lights up because the magnetic flux linkage through the loop varies with time.


18

31 The magnetic flux linkage through a coil varies with time as shown.

Which graph shows the variation with time of the e.m.f. generated by the coil?

A

B

C

D


19

32 The figure below shows the variation with time of a periodic current.

What is the root-mean-square value of the current?

A 3.35 A

B 3.75 A

C 3.97 A

D 4.50 A

33 A pure resistor has an alternating supply connected across it. The frequency of the supply is varied while the r.m.s. voltage is kept constant.

How is the mean rate of heat dissipated across the resistor related to the frequency?

A proportional to (frequency)2

B proportional to frequency

C proportional to (frequency)½

D Independent of frequency

34 The de Broglie wavelength of a particle that has kinetic energy K is λ. The wavelength λ is proportional to

A −12K

B −1K

C 12K

D 2K


20

35 Some energy levels for a hydrogen atom are shown in the diagram.

In the spectra below, the frequency scale is linear and increases to the right.

Which spectrum best corresponds to the possible transitions when the electrons of an excited hydrogen atom fall to the -3.41 eV level?

A

B

C

D


21

36 The diagram below shows the wave function ψ(x) of an electron.

Which statement about the electron is false??

A The probability of finding the electron is the lowest at O.

B The probability of finding the electron is zero at Q and R.

C The probability of finding the electron is higher at S than at P.

D The probability of finding the electron between P and S is less than one.

37 Which diagram correctly shows the three possible processes: excitation, stimulated emission and spontaneous emission between the energy levels in a 4-level laser system?

A B

C D


22

38 Which of the following statements below on intrinsic semiconductors is true?

A The total current flow is the sum of both ‘hole’ and ‘electron’ currents.

B There are more electrons in the conduction band than there are holes in the valence band.

C The valence band is completely filled and the conduction band is partially filled.

D The valence band is completely filled and the conduction band is empty at room temperature.

39 Radiation from a radioactive source enters an evacuated region in which there is a uniform magnetic field directed into the plane of the diagram. This region is divided into two by a sheet of aluminium about 1 mm thick. The curved, horizontal path followed by the radiation is shown in the diagram below.

Which of the following correctly describes the type of radiation and its point of entry?

Type of radiation Point of entry

A alpha Y

B alpha Z

C beta Y

D beta Z


23

40 To initiate nuclear fission on a nucleus, a particle is usually needed to knock onto the nucleus. The particle is suggested to be a

A neutron since the mass is comparable to that of the nucleons.

B neutron since it has no electrical interaction with the nucleons.

C proton since there will be strong nuclear forces with the nucleons.

D proton since the mass is comparable to that of the nucleons.

End of Paper

©JJC 2015 9646/JC2 Preliminary Exam P2/2015 [Turn Over

JURONG JUNIOR COLLEGE JC2 Preliminary Examination 2015

Name Class 15S

PHYSICS Higher 2

Structured Questions

Candidates answer on the Question Paper. No Additional Materials are required.

9646/2

2 Sep 2015

1 hour 45 mins

READ THESE INSTRUCTIONS FIRST 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 paper clips, highlighters, glue or correction fluid. Answer all questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

For Examiner’s Use

1

2

3

4

5

6

7

8

9

Total



2


2 at2


φ = −Gm

r



2 kT



Qε rπ4


where k = 2

2

8 ( )m U Eh

π −


λ = 1/2

0.693t


3

1. A zoologist studying the wildlife in Africa decided to model the thigh bone of a male

African Elephant as a physical pendulum pivoted at the hip joint of the elephant.

The period of the physical pendulum can be expressed as

IT=2πmgh

where T is the period of oscillation,

I is the rotational inertia of the pendulum about the pivot which has a unit of kg m2,

m is the mass of the thigh bone,

g is the acceleration of free fall and

h is the distance of the centre of gravity of the bone from the pivot.

(a) Show that the equation is homogeneous in terms of base units. [1]


4

(b) If the value of I is (0.2085 ± 0.0001) in kg m2, and m and h are measured to be (4.1 ± 0.5) kg and (47.0 ± 0.1) cm respectively, calculate T and express it with its associated uncertainty.

T = ( ± ) s [4]

2 (a) Define electric potential at a point.

[1]


5

(b) Two charged spheres of radius 2.0 mm are held 4.00 cm apart (centre-to-centre). Fig. 2 shows the variation with displacement x, of the electric potential V, between the two charged spheres.

V / V

x / cm

Fig. 2

Position of charged sphere


6

Using Fig. 2, determine

(i) the magnitude of the electric field strength at x = 1.00 cm and state its direction,

magnitude of the electric field strength = N C-1 [2]

direction of electric field strength is [1]

(ii) the charge on each sphere.

charge on each sphere = C [2]

3. Fig. 3 shows a region PQRS of a uniform magnetic field directed downwards into the plane of the paper.

Fig. 3


7

Electrons, all having the same speed, enter the region of the magnetic field.

(a) On Fig. 3, show the path of the electrons as they pass through the magnetic field, emerging from side QR. [2]

(b) A uniform electric field is also applied in the region PQRS so that the electrons now pass undeflected through this region. On Fig. 3, mark, with an arrow labelled E, the direction of the electric field. [1]

(c) The undeflected electrons in (b) each have charge - e, mass m and speed v. State and explain the effect, if any, on particles entering the region PQRS of the same magnetic and electric fields as in (b) if the particles each have

(i) charge - e, mass m and speed 2v,

[2]

(ii) charge +e, mass m and speed v.

[2]


8

4 In a photoelectric effect experiment, the maximum kinetic energy Ek,max of the ejected

photoelectrons is measured for various wavelengths, λ of the incident light.

Fig. 4 shows the variation with wavelength λ, of the incident light, of Ek,max.

Fig. 4

(a) (i) From Fig. 4, state and explain one piece of evidence that supports the theory that light has a particulate nature.

[2]

Ek,max / eV

λ / nm 0 50 100 150 200 250

5.0

10.0

15.0

20.0


9

(ii) Describe briefly how the maximum kinetic energy of the emitted electrons may be measured experimentally.

[3]

(b) Using a suitable point from Fig 4, determine the work function of the metal used.

work function = eV [3]

5 A junction is formed between slices of p-type and of n-type semiconductor material, as shown in Fig. 5.

Fig. 5

(a) On Fig. 5, draw an arrow to show the direction of movement of holes as the two slices are brought into contact. [1]

p-type

material

n-type

material


10

(b) Describe the origin of the depletion region at the junction.

[4]

(c) On Fig. 5, draw the symbol for a battery connected so as to increase the width of the depletion region. [1]

6 (a) The tip of a scanning tunnelling microscope (STM) is brought close to but does not touch the surface to be scanned. A small current flows between the tip and the surface. Explain briefly why there is a current using the concept of quantum tunnelling.

[2]


11

(b) An electron is moving in the x-direction with a speed of 2.05 × 106 m s-1. Given that the precision in measuring the speed of the electron is 0.50 %, determine the minimum uncertainty with which the position of the electron along the x-direction can be simultaneously determined.

minimum uncertainty of electron’s position = m [2]


12

7 Many unstable parent nuclei undergo radioactive decay, a random and spontaneous process, to give a daughter product which is itself radioactive. This may give rise to a radioactive series where there may be ten or more different radioactive daughter products.

The variation with time t of the number N of different nuclei in a radioactive sample is illustrated in Fig 7. The parent nucleus P decays to a daughter nucleus D, which in turn, produces a further daughter S which is stable as shown in the following process below.

P D + 0-1e S + 4

2He + γ

Initially, there are 50 x 105 nuclei of P in the sample.

(a) (i) On Fig. 7, label with the letter S the line representing the variation with t of the number of nuclei N of the stable further daughter S. [1]

Fig. 7

(ii) Determine the half-life of product D.

half life = years [2]

N / 105

50 40 30

20 10 0

0 50 100 150 200 250 300 350 t / year


13

(iii) State the time at which the activity of the daughter product D is maximum.

time = years [1]

(iv) Calculate the maximum activity of the daughter product D.

maximum activity = yr-1 [2]

(v) Explain why the number of nuclei of the daughter product D increases initially.

[1]

(vi) The relative activities of the parent isotope and the daughter products may be used as a means of determining the age of the sample.

Suggest why this technique may provide reliable results for ages up to about 300 years but for an age of about 1000 years, the method would be far less reliable.

[1]

(b) Describe qualitatively the direct effects of the emitted alpha particles on cells.

[2]


14

8. The hull is the main body of a boat. The load waterline length LWL refers to the horizontal length of a hull at the water’s surface when a boat is carrying a normal load. It is a significant factor in establishing how fast a boat can go.

As a boat first begins to move, rather small waves are generated at the bow – the front of the boat – with a pattern of these small waves moving back along the side of the boat, reaching the stern – the back of the boat. As the boat moves faster, the wavelength of the bow wave increases.

Hull speed vhull is the speed of the boat such that the wavelength of the bow wave of the boat is equal to its load waterline length LWL.

If the boat moves faster than the hull speed vhull, the wavelength of the bow wave becomes even longer and the stern of the boat will begin to fall into the trough so that the boat will be angled upwards as shown in Fig 8.1.

Fig 8.1

(a) (i) On Fig. 8.1, label clearly the load waterline length LWL of the boat at hull speed vhull.

[1]

(ii) Give two reasons why it is inefficient for the boat to move above its hull speed vhull.

Reason 1:

Reason 2:

[2]


15

(b) The variation with LWL of vhull for a typical boat is shown in Fig. 8.2.

Fig 8.2 The relationship between vhull and LWL is thought to follow the expression

vhull = 1n

WLkL

where k is a constant and n is an integer.

6.0 4.0 8.0 10.0 12.0 14.0 LWL / m

vhull / m s−1

16.0

2.5

3.0

3.5

4.0

4.5

5.0

2.0


16

Data from Fig. 8.2 are used to obtain values of lg vhull and lg LWL. These are plotted on the graph of Fig. 8.3.

(i) Use Fig. 8.2 to determine lg vhull for LWL = 12.0 m.

lg vhull = [1]

(ii) On Fig. 8.3,

1. plot the point corresponding to LWL = 12.0 m,

2. draw the best fit line for all the points. [2]

lg (LWL / m)

lg (vhull / m s−1)

Fig. 8.3

0.7 0.6 0.8 0.9 1.0 1.1 1.2

0.40

0.45

0.50

0.55

0.60

0.65

0.35

0.70


17

(iii) Use the gradient of the line drawn in (b)(ii)2 to determine n.

n = [2]

(iv) Using your answer in (b)(iii), determine the magnitude of k.

magnitude of k = [2]

(v) Determine the SI base units for k.

SI base units = [1]


18

(c) The Formidable-class frigates are the latest boats to enter into service with the Republic of Singapore Navy. They have a load waterline length of 0.11 km.

(i) Determine the hull speed of a Formidable-class frigate.

hull speed = m s-1 [1]

(ii) Suggest why the Formidable-class frigate is designed to achieve a higher maximum speed than its hull speed.

[1] (d) Large ships such as cargo ships and oil tankers often have a protruding bulb at the

bow of the ship just below the waterline, known as a bulbous bow. A bulbous bow is shown in Fig. 8.4, and can generate waves similar to the bow of the ship.

Fig. 8.4 Use the principle of superposition, suggest how bulbous bows help ships to achieve

better fuel efficiency than similar vessels without them.

[1]

bow of ship

bulbous bow


19

9 As a bar magnet is dropped through a coil, an e.m.f. is induced in the coil. The maximum

e.m.f. E is induced as the magnet leaves the coil with speed v. It is suggested that E is directly proportional to v.

Design a laboratory experiment to the relationship between E and v. You should draw a diagram showing the arrangement of your equipment. In your account you should pay particular attention to (a) the identification and control of variables,

(b) the equipment you would use,

(c) the procedure to be followed,

(d) how the relationship between E and V is determined from your readings

(e) any precautions that would be taken to improve the accuracy and safety of the

experiment.


20

Diagram


21


22

End of Paper

©JJC 2015 9646/JC2 Prelim Exam P3/2015

JURONG JUNIOR COLLEGE 2015 JC2 Preliminary Examination

Name Class 15S

PHYSICS Higher 2

Longer Structured Questions

Candidates answer on the Question Paper. No Additional Materials are required.

9646/03

14 September 2015

2 hours

READ THESE INSTRUCTIONS FIRST 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. Section A Answer all questions. Section B Answer any two questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

For Examiner’s Use

1

2

3

4

5

6

7

8

Total


© JJC 2015 9646/JC2 Prelim Exam P3/2015 [Turn Over

2


2 at2


φ = −Gm

r



2 kT



Qε rπ4


where k = 2

2

8 ( )m U Eh

π −


λ = 1/2

0.693t


3

Section A Answer all the questions in this Section.

1 (a) Define acceleration.

[1]

(b) A train driver Anthony spots another train, its tail 100 m ahead of him on the same track. Anthony’s train is moving at a speed of 72 km h-1 and the other train is moving at a constant speed of 54 km h-1 in the same direction.

(i) State the maximum speed of Anthony’s train, in m s-1, in order to avoid a collision at the time his train has closed the gap of 100 m between the two trains.

speed of Anthony’s train = m s-1 [2]

(ii) Sketch the distance-time graph of Anthony’s train. [1]


4

(ii) Determine the minimum deceleration Anthony’s train must have in order to just avoid a collision.

minimum deceleration = m s-2 [3]

2 (a) Define work done by a force.

[1]

(b)

Fig. 2.1 shows two blocks A and B connected by a light inextensible cord passing over a frictionless pulley. When both blocks are released, block A starts to move from rest along a rough plane which is inclined at 30o to the horizontal. The speed of block B just before hitting the ground is 4.0 m s-1

Calculate the average friction force acting on block A.

Fig. 2.1

2.0 kg

6.0 kg 5.0 m 30o

AB


5

frictional force = N [4]

3 (a) Fig. 3.1 shows a particle, of mass 0.30 kg, being suspended and rotated from a position A by an inextensible string of length of 2.0 m.

(i) In Fig. 3.1, draw the resultant force acting on the particle when it is at position C. [1]

(ii) Determine the minimum kinetic energy with which the particle should be projected from position B, in order for the string to be just taut at point D (i.e. highest position).

kinetic energy = J [3]

Fig. 3.1

D

A C

B

2.0 m


6

(b) A binary star system consists of two stars with masses M1 and M2 as shown in Fig. 3.2. The centres of the two stars are separated by a distance R = 1.2 x 1010 m. The diagram is not drawn to scale.

Fig. 3.3 shows the variation of the gravitational potential ϕ with distance x from the centre of star M1.

A particle is launched with kinetic energy Ek from the surface of star with mass M2. The particle arrives at the surface of the star of mass M1.

- 0.5

- 0.7

- 0.9

- 1.1

- 1.3

ϕ / x 1012 J kg-1

x / x 109 m4.0 2.0 6.0 8.0 10.0 0

Fig. 3.3

Surface of star with mass M1

Surface of star with mass M2

Fig. 3.2

R

x

M1 M2


7

(i) Explain whether the kinetic energy of the particle at the surface of M1 is less than, equal to, or larger than Ek,

[2]

(ii) 1. Determine the distance x at which the gravitational field strength due to the two stars is zero.

x = m [1]

2. Hence determine the ratio 1

2

MM

.

ratio = [3]

4 (a) Define specific heat capacity.

[1]


8

(b) A cake of mass 0.90 kg is baked in an oven at a temperature of 180°C. It is then taken out of the baking tin onto a rack to cool in a kitchen of 25°C. The oven of volume 0.10 m3 also cools down from 180°C to 25°C.

(i) Take the specific heat capacity of the cake to be 990 J kg-1 K-1.

Calculate the energy released from the cake in cooling.

energy released = J [2]

(ii) The pressure in the oven remains constant at the atmospheric pressure of 1.01 x 105 Pa. Assume the air behaves as an ideal gas. The molar mass of air is 0.030 kg mol-1.

Calculate the change in the mass of air in the oven between the two temperatures.

change in the mass of air = kg [3]


9

(iii) Calculate the root-mean-square speed of the air molecules at 25°C.

root-mean-square speed = m s-1 [2]

5 (a) (i) Define electromotive force of a source.

[1]

(ii) Distinguish between electromotive force and potential difference.

[2]

(b) Fig. 5.1 shows a circuit containing a thermistor and three fixed resistors of values 100 Ω, 120 Ω and 200 Ω. The voltmeter connected between A and B has infinite resistance. The battery has e.m.f. 6.00 V and negligible internal resistance. The voltmeter reads zero when the ambient temperature is 25 °C.


10

Fig. 5.1

(i) State the resistance of the thermistor when the voltmeter reads zero.

resistance = Ω [1]

(ii) As the temperature rises above 25 °C, the voltmeter starts to register a reading. Deduce whether the potential at A is higher or lower than the potential at B.

[3]

(iii) Determine the two possible values for the resistance of the thermistor when the voltmeter registers a reading of 1.0 V.

resistance = or Ω [3]


11

Section B

Answer two questions from this Section.

6 (a) State Newton's second and third laws of motion.

Newton’s second Law:

Newton’s third Law:

[4]

(b) Define force.

[1]


12

(c) Using sketches, with labelled arrows showing the directions of velocity v and acceleration a, describe situations in which an object

(i) has an acceleration at right angles to its velocity,

(ii) has an acceleration in the opposite direction to its velocity.

Add to your sketches a labelled arrow showing the direction of the resultant force acting on the object in each case. [4]

(d) (i) State the principle of conservation of momentum.

[1]

(ii) Does the principle apply in cases where two colliding objects lose kinetic energy as a result of sticking to one another at the point of collision?

Explain your answer with reference to Newton's third law.

[2]


13

(e) A particle of mass 1.20 kg collides head -on and elastically, with a ball of mass 0.60 kg moving with a speed 0.2 m s-1 in opposite direction. The ball moves off with a speed of 0.1 m s-1. Calculate for the particle

(i) its initial speed,

initial speed = m s-1 [4]

(ii) its final speed.

final speed = m s-1 [2]

(f) Suggest, with a reason, if the equations used in (e) would apply if the collision took place on a rough surface.

[2]


14

7 (a) Wave–particle duality is the concept that all matter and energy exhibit both wave-like and particle-like properties. An electron diffraction tube shown in Fig. 7.1 can be used to show the wave nature of particles. Electrons are accelerated from rest at the filament towards the target by a potential difference of 4.5 kV.

When the electrons pass through a graphite target, an interference pattern is observed on the screen as shown in Fig. 7.2. The first-order maximum of the interference pattern occurs at an angle of 10° from the straight-through position.

(i) State the meaning of diffraction.

[1]

(ii) Show that the de Broglie wavelength of the electrons is approximately 1.8 x 10-11 m. [2]

(iii) Estimate the separation of the atoms in the graphite.

separation = m [2]

Fig. 7.1

4.5 kV

Fig. 7.2


15

(iv) Suggest why if the electrons are accelerated from rest at the filament towards the target by a potential difference much lower than 4.5 kV, no interference pattern is observed on the screen.

[2]

(b) The following experiment is set up to determine the frequency of a vibrating dipper. This vibrating dipper causes a water wave of small amplitude to travel in a tank of water d = 2.6 cm deep, as shown in Fig. 7.3.

The mean speed v of the travelling water wave in shallow water is dependent on both d and the acceleration of free fall g and is given by =v gd .

Fig. 7.3

(i) Calculate the frequency of the vibrating dipper, given that the distance

between 2 adjacent crests of the water wave is 0.025 m.

frequency = Hz [2]

(ii) Explain why the water wave needs to have a small amplitude.

[1]

vibrating dipper

d = 2.6 cm

water tank

C direction of wave travel


16

(c) Two coherent sources A and B, which are in anti-phase with each other, emit wave of wavelength 40.0 mm. (Not drawn to scale)

The amplitude of the wave from source B is twice that of source A.

A detector is placed at the point P where it is 1.00 m from A and 1.18 m from B as shown in Fig. 7.4.

Fig. 7.4

(i) State the type of electromagnetic radiation that is emitted by sources A and B.

radiation is [1]

(ii) Suggest a suitable distance between sources A and B.

distance = m [1]

(iii) State and explain whether constructive interference or destructive interference takes place at P.

[2]

(iv) Determine the ratio of the intensity at P to the intensity at O.

ratio = [2]


17

(ii) State how wind instruments A and B differ from wind instrument C, in terms of

the type of air column they possess.

[1]

(iii) Sketch the waveform of the 1200 Hz sound wave produced in the air column of instrument B. Your answer should include a sketch of the air column of instrument B.

[1] (iv) Sketch the waveform of the 1200 Hz sound wave produced in the air column

of instrument C. Your answer should include a sketch of the air column of instrument C.

[1]

(d) Different musical instruments do not sound the same even if the same note is played. Fig. 7.5(a), (b) and (c) show the frequencies produced when the same note is played by wind instruments A, B and C, respectively.

(i) State one similarity between the note produced by the three wind instruments.

[1]

Fig. 7.5(a) Fig. 7.5(b) Fig. 7.5(c)


18

8 (a) (i) State what is meant by simple harmonic motion.

[2]

(ii) A student ties a pendulum bob to a piece of long string and uses the pendulum to perform small oscillations. The position of the bob at 0.10 s intervals is shown in Fig. 8.1.

Fig. 8.1

Fig. 8.1 shows exactly one half-cycle of the bob’s motion.

If the motion is simple harmonic, determine the maximum speed vmax of the bob.

vmax = m s-1 [3]


19

(b) A protective device in a mains circuit consists of a transformer with two primary coils A and B and a secondary coil, as shown in Fig. 8.2. The primary coils each have the same number of turns and are wound in opposite directions on the core.

Fig. 8.2 The mains supply is connected in series with the two primary coils and the electrical appliance. The secondary coil is connected to an electromagnetic switch.

(i) State Faraday’s law of electromagnetic induction.

[2]

(ii) 1. At one particular moment, the live lead is positive with respect to the neutral lead.

On Fig. 8.2, mark arrows to indicate the direction of the magnetic field in the transformer core due to the primary coil A alone (label this arrow A), and the direction of the magnetic field in the transformer core due to the primary coil B alone (label this arrow B). [1]

2. Hence state and explain if there is any e.m.f. induced in the secondary coil.


20

[3]

(c) Fig. 8.3 shows a region of magnetic field having a uniform flux density of 2.0 x 10-4 T and directed out the paper. A wire coil placed at P is in the plane of the paper and away from the field. The coil has 200 turns, a total resistance of 2.0 Ω and an area of 10 cm2.

The coil is moved from P to R in 0.20 s.

Fig. 8.3

(i) Calculate the amount of charge which flows in the coil.

charge = C [2]

(ii) State and explain if there would be any change in the amount of charge if the number of turns in the coil is increased.

[2]


21

(d) An ideal transformer has 5000 turns in its primary coil. It is used to convert a mains supply of 230 V to an alternating voltage having a peak value of 12.0 V.

(i) Calculate the number of turns in the secondary coil.

number of turns = [2]

(ii) The secondary coil is connected in series with a resistor R.

The variation with time t, in seconds, of the potential difference at the secondary coil is given by the expression

V = 12.0 sin(380t)

1. Determine the frequency of the supply.

frequency = Hz [1]

2. To prevent overheating, the mean power dissipated in R must not exceed 300W. Calculate the minimum resistance of R.

minimum resistance = Ω [2]

End of Paper

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