stpm trial 2009 phy q&a (n9)

8/14/2019 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 STPMValues of constants

*************************************************************************

Speed of light in free space c = 3.00 x 108 ms-1

Permeability of free space o = 4 x 10-7 Hm-1Permittivity of free space o = 8.85 x 10-12 Fm-1Magnitud 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 before Q and at the same distance from the building.

B at the same time as Q and at a nearer distance to the building.

C at the same time as Q and at the same distance from the building as Q.

D 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 0 N 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 trolleys 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 moment of inertia

B linear momentum

C angular momentum

D angular velocity

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

A Mass

B Shape

C Angular acceleration

D Mass distribution

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

Find the additional forces which act on the board when a diver of 750 N stands on the

right hand end.

At X (Downwards) At Y (Upwards)

A 900 N 1500 N

B 1125 N 1875 N

C 1375 N 1875 N

D 1375 N 1500 N

5 m

750 N

Y

2 m

X

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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 Gravitational potential energy

B Orbital linear speed

C Centripetal acceleration

D 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

txy

20cos4

sin2= , with x and y in centimeter, and t in s. What is the

distance between two consecutive nodes in the stationary waves?

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 intermoleculardistance r for a diatom.

Which of the following is true for the intermolecular forces at point P and at point Q?

Point P Point Q

A Attraction Zero

B Zero Attraction

C Zero Repulsion

D 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?

0

Force

Strain

0

Stress

Strain

0

Stress

Extension

0Extension

A B

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18.The figure below shows a glass rod of diameter 2r. One end of the rod has a surfacewhich is a hemisphere of radiusr. The refractive index of the glass isn. A point

object O is at a distance u from the end of the rod. The imageIdue 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?

An

rn )2( +

B)1(2

)2(

+

n

rn

C2

)1(2

+

n

rn

D2)1(2

n

rn

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

A4

dB

3

dC

2

dD

4

3d

20.A beam of light which consists two different wavelength and 2( > 2) is incident

normally on a piece of diffraction grating. The second order line for and the third

order line for 2 overlap. What is the ratio of2

1

?

A 1.5 B 2.0 C 2.5 D 3.0

2r

r

u v I

n

O

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

In the direction of the first minimum, the path differencex between the raysPQ

andRS is

A4

B2

C D 2

3

22. Nitrogen gas at a pressure of 1.01 105 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 510 Pa is

1.40 kg m 3 . Find the mean kinetic energy of an oxygen molecule.

( The relative molecular mass is 32 )

A 3.71 1023 J

B 4.71 1027 J

C 5.75 1021

JD 6.75 10

23J

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

S

x

P

Q

R

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27. The circuit below includes an operational amplifier.

Given thatR 1 = R 2 = R 3 = R 4 , which of the following expressions gives the magnitude of

the output voltage V o ?

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.

A30.8 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 copperk = 380 W m 1 K 1 : specific latent heat of fusion of ice =

333 kJ kg 1 )

A 0.04 kgB 0.08 kg

C 2,48 kg

D 3.56 kg

A V1

+ V2

+ V3

B ( V 1 + V 2 + V 3 )

++321

4

RRR

R

C V 1

4

1

R

R+ V

2

4

2

R

R+ V

3

3

4

R

R

D ( V 1 + V 2 + V 3 )

++

4

321

R

RRR

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28. A point charge QB is moved round another positive point charge QA on a circular

path of radiusr. The work done on the charge QA in making one complete

revolution is

A. A B (2 )4

Q Qr

B.2

A B (2 )4

Q Qr

r

C.2

A B (4 )4

Q Qr

r

D. Zero

29. A circle of radiusR is drawn in side a uniform electric fieldE as shown.

VA, VB, VC and VD are respectively the potentials of points A, B, C and D

at the periphery of the circle.

Which of the following best describe the relationships between VA, VB, VC and VD?

A. VA= VC; VB = VD. B. VA= VC; VB VC; VB = VD. D. VA


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31. Two capacitors of capacitance 2 F and 3 F are joined in series and thiscombination 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 SP

U

U ?

A. 2 : 3 B. 3 : 2

C. 6 : 5 D. 6: 25

32. What is the relationship between the drift velocity Vd of electron

and the applied electric fieldE?

A. VdE2 B. VdE.C. Vd E D. Vd 1

E

33. The resistivity of iron is 1 107

.m. The resistance of the iron wire is 1 .If the diameter and length of the wire are both doubled,

what is the new resistivity of the wire?

A. 1 107

.m. B. 2 107.m.C. 4 10

7.m. D. 8 107.m.

34. The figure shows the current distribution in a part of an electrical circuit.

Find the value ofI?

A. 1 A B. 2 A

C. 1.5 A D. 3 A

1 A

1 A3 A

2 A

2 A

I

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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. 2R B.2

R

C.3

2R D.

2

3R

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 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 in the range 0 to 90?

2R 2R R

C

DA B

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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?

Electric field Magnetic field

A no no

B no yes

C yes no

D yes yes

38. A uniform magnetic field of flux density B passes normally through a plane

area A. In this plane lies a coil of eight turns of wire, each of area A41 .

What is the magnetic flux linkage for the coil?

A BA4

1B BA C 2BA D 8BA

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

The solenoid currentIis varied with timet 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 betweenB andIis B=on I.

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

time?

40. There is a sinusoidal alternating current in a resistor. What is the mean

power dissipated in the resistor?

A 2)(max2

1currentimum C

2)(max

2

1currentimum

B )(max2

1powerimum D )(max

2

1powerimum

41. A sinusoidal supply of frequency 100 Hz and r.m.s. voltage 12V is connected to a

2.2 F capacitor. What is the r.m.s. value of the current?

A 0.42A B 5.5A C 17A D 26A

42.Which of the following quantities of the incident light affect the maximum kineticenergy 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 particlesB. the size of electrons is very smallC. the electrons have much shorter wavelengthD. the image observed in the electron microscope is monochrome.

D

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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

B

C

D

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

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

atomic plane spacing.

Increasing wavelength

Imncreasing wavelength



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46. The figure below shows the paths of the ions of the isotopes of an element in a

mass spectrometer

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

A 2 : 4 : 28 B 11 : 12 : 14

C 18 : 20 : 24 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)

Without source

(Background radiation)

With source

10 8 48

30 8 18

90 8 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 21H 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

28 cm

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49. In general, the fission of a heavy nuclear will produce two small nuclei, two or three

neutrons, several -particles and a little -radiation. It is always true that the

product

A have total rest mass that is greater than the original mass of the nucleus.B have most of the kinetic energy originated from part of the loss in energy.

C move in exactly opposite directions

D 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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*This question paper is CONFIDENTIAL until the examination is over. CONFIDENTIAL*

Section A [40 marks]

Answerallthe questions in this section.

1. A student suggests that the force F acting on a vertical wall due to a horizontal jetof l iquid st riking t he wall i s given by t he expression F = kAv where k is adimensionless constant, , A and v represent the density of the liquid, the crosssectional ar ea of t he jet a nd sp eed o f t he jet r espectively. I s the ex pressiondimensionally correct?

[5 marks]

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

(i) Using Newtons law of motion, explain why an external force is needed toapply 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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3. The figure bel ow sh ows a wheel of r adius 30 cm t hat i s brought t o r estuniformly from an angular velocity of 2.0 revolutions per second. If the beltthat passes through the wheel is 25 cm,

Calculate

(a) the number of revolutions completed. [2 m arks]

(b) The angular acceleration[2 marks]

4. (a) Calculate the electric potential midway between two identical charges,

+20 C, placed 30 cm apart in vacuum.

Take the value ofo = 8.9 1012 F m1. [2 marks]

.

(b) (i) Explain what is meant by an equipotential surface.

.

.[1 mark]

Belt

Wheel

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(ii) Explain why a place anywhere in an electric field will be an equipotential surface.

..

...

.

[2 marks]

5. Two welll-lagged uniform copper rods and well-lagged uniform iron rod, each of

cross-section area 6.0 2510 m and length 12 cm, are joined end-to end as shown inthe figure below. The free ends are maintained at 2000 C and 00 C respectively.

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

K-1

and that of iron is40 W m

-1K

-1.

Calculate

(i)21 and [ 4 marks]

(ii) the rate of heat flow through the composite rod. [2 marks]

CopperIronCopper2000

C 00

C

1 2

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6. The di stance b etween t he pl ates o f a parallel capacitor is 5.0 mm and the area ofeach plate is 2.0 mm2. The plates are in a vacuum. The potential difference of 1.0 104 mm is applied across the plates.

Find:

(a) the capacitance, [3 marks]

(b) the charge on each plate, [2 marks]

7. The Bohr energy states En for the hydrogen atom is given by

3...)2,1,(neV6.132

==

nEn

(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

+He

4

2 .

[2 marks]

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8. (a) Two similar coils A and B of insulated wire are wound on to a soft-ironcore, as in

Figure 1.1When the current I in coil A is switched on and then off, the variation withtime 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. Einduced in coil B.

[3 marks]

(b) Explain why the transformer could not be used to step down the potentialdifference of a direct current supply.

[2 marks]

I

O

O

E

t

t

Figure 1.2

Figure 1.3

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Section B

Answer any fourquestions 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 mark]An object of mass 2.0 kg is at rest on a r ough horizontal plane. At the instant t = 0, ahorizontal force F a cts on t he obj ect, c ausing t he object t o m ove at co nstantacceleration i n a s traight l ine. A t t = 1 0 s, the a pplied force i s removed. The objectdecelerates and comes to rest after moving for a total time of 15 s. The graph in figurebelow show how the velocity vof the object varies with time t.

(a) Determine the frictional force, which is assumed to be constant, that acts on theobject 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 sand t = 15 s. on the graph show also the frictional force F f.

[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.[3 marks]

(ii) by the frictional force Ffbetween t = 0 s and t = 15 s.[2 marks]

v/m s-1

5 10 150

10

t/s

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10. (a) The figure below shows two electrons separated by a distance of3.0 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

-19C and

the permittivity of free space = 8.85 x 10 -12 F m -1.

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 twoelectrons can be neglected when compared to their resultant force?

[2 marks]

(b) i. Write an equation for Newtons universal gravitational law. Statethe 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 gravitationalconstant G is 6.67 x 10-11 N m2 kg-2. Estimate a value for the massof Earth.

[2 marks]

iii. Show that the gravitational field strength at a point of height h from

the surface of the Earth is given by( )2hRGM

g+

= in which R is the

radius of the Earth.[3 marks]

iv. Find the escape velocity of the earth. [2 marks]

Electron Electron

3.0 x 10-10

m

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11. (a) State three differences between progressive and stationary waves.[3 marks]

(b) Explain the meaning of intensity of a progressive wave andstate its SI unit.

[2 marks]

(c) State whether stationary waves possess intensity. Explain youranswer.

[4 marks]

(d) A circular progressive wave is produced on the surface of water from apoint O by vibrating a dipper with constant amplitude. Explain why theamplitude of the wave decreases as the distance of the wavefront from Oincreases, by assuming that the absorption of energy by the medium isnegligible. [4 marks]

(e) At a distance r from O, the amplitude of the wavefront is A. Calculate theamplitude of the wavefront at a distance 2r from O.

[2 marks]

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

(b) There are two situations in which a charged particle in a magnetic fielddoes not experience a magnetic force. State these two situations.

[2 marks](c) Figure shows a beam of electrons entering a magnetic field of magnetic

flux density 8.4 mT. The electrons are traveling with velocity3.4 107 m s-1 at right angles to the field.

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]

(iv) Sketch the path traveled within and beyond the field. [2 marks]

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c) Charged particles from the Sun, on approaching the Earth, may become trappedin the Earths magnetic field near the poles, as shown in Figure. This can causethe 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 wherethe magnetic flux density is 6.0 10-5 T.

(i) For a charged particle of charge to mass ratio e/m, deduce an expressionfor its speed v when traveling in a circle of radius r within a magnetic fieldof flux density B.

[2 marks]

(ii) Use your answer to (i) and the information about the path of the particlesto show that the charged particles causing the aurora cannot be electrons.

[2 marks]

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

(a) Identify the two distinct features of the spectrum and explain how they areproduced.

[5 marks](b) Copy the graph above (with the labels) and sketch new graphs of the X-

ray spectrum produced when

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

iii. the target metal is replaced with another element with higher atomicnumber.

[6 marks](c) The inter-planar spacing of a crystal of NaCl is 0.282 nm. It is found that afirst-order Bragg reflection of a monochromatic beam of X-rays occurs atan angle of 11

o.

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

[4 marks]

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14 (a) Explain what do you understand by the term

(i) mass defect(ii) activity of radioactive atom(iii) nuclear fusion [3 marks]

(b) C136

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

an experiment to produce N137 . 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 U235 , and the nuclear assumedto be represent by the nuclear fission reaction below

( )nBrLanU 108535148571023592 3+++

(i) State what is the role played by the neutrons produced in the abovenuclear reaction [1 mark]

(ii) Calculate the energy released by each of the U235 atom which undergoesthe fission. [3 marks]

(iii) Calculate number of U235 atoms used by the reactor in a period of12 hours if the reactor is operating at maximum power [4 marks]

[ Mass of U235 = 235.0439u ; La148

57 = 47.9314u ; Br8535 = 84.9156u ; n10 = 1.0097u ]

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ANSWER TRIAL EXAM PHYSICS STPM PAPER 1 2009

1. C 2. C 3. C 4. A 5. B

6. B 7. C 8. B 9. A 10. D11. B 12. D 13. A 14. D 15. D

16. D 17. C 18. B 19. C 20. A

21. C 22. C 23. C 24. A 25. A

26. B 27. A 28. D 29. B 30. B

31. D 32. B 33. A 34. A 35. B

36. D 37. B 38. C 39. C 40. D

41. D 42. C 43 .C 44. D 45. D

46. B 47. B 48. D 49. B 50. B

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ANSWERS STRUCTURE

1. Let F = k m An vp

MLT-2 = [ML-3]m [L2]n [LT-1]p ( 1 m )= M

mL

-3m+2n+pT

-p

Compare m = 1-3m+2n+p = 1

P =2

Solving, we get m =1, n = 1, p = 2 ( 2 m )and F = kAv2 ( 1 m )

Hence, the expression F = kAv suggested by the student is incorrect. ( 1 m )

2. (a) According to the Newtons first law of motion, an object at rest will continue to remain at resor if moving, will continue to move with constant velocity along a straight line, if no externalforces act on the object. ( 1 mark )

An object moving in a ci rcular path always change i ts direction, so, an ex ternal force ineeded to apply to the object. ( 1 mark )

(b) The force is perpendicular to the velocity ( 1 mark )and always point towards the centre of the circle. ( 1 mark )

(c) Centripetal force ( 1 mark )

3. a. The number of revolutions completed = 3.1330.02

25=

b. 22

0

2 += ; 0 = 2.02 + 2 (13.3); 2/secrevolution5.0=

4. (a) V=6 6

20 10 20 10

4 ) 4 )

12 2 12 2(8 9 10 ) (15 10 (8 9 10 ) (15 10

+ . .

= 2.38 106

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

(b) (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 reducethe potential differences to zero. (1 mark)

Total marks for 1. b (ii) : (2 marks)

1 mark

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5 (a) (i) Since the rod are well-lagged, the rate of heat flow is constant in each rod and isthe same in the copper and the iron rods.

Applydx

dkA

dt

dQ =

For the copper-iron pair

)(105.0200211

=

211105.0105.0200 =

200 = 1.1051 2105.0 ..(1)

For the iron-cooper pair on the right

)(105.0212 =

12 105.0105.1 = ..(1)

Substitute copper iron

200 = 1.1051 - 0.105

1

105.1

105.0.(1)

C181o1 =

=2 17.2 Co ...(1)

(ii) Rate of heat flow

=

xkA

t

Q 21 ..(1)

For the copper rod on the left

=

2

5

1012

181200)106.0(380

t

Q

= 3.61 J s

1

.(1)

6. (a) Capacitance of the parallel plate capacitor

C=A

d

[1 mark]

=12

3

8 85 10 2

5 10

.

F [1 mark]

= 3.54 109

F. [1 mark]

(b) The charge on each plate.

Q=CV

= (3.54 109

) (1 104) C [1 mark]

= 3.54 105

C [1 mark]

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7. The Bohr energy states En for the hydrogen atom is given by

eV6.132n

En = ( n = 1,2,3..)

(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 for helium ion+He

4

2 . [2 marks]

8. (a)

(b) 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.

I

O

O

E

t

t

Figure 1.2

Figure 1.3

Ionisation energy = 1EE

= 1

6.13

0

= 13.6 eV

1

1

1

Z=2

2 6.134n

En

=

=2

4.54

n eV

1

1

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9. 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 F facts on the objectduring 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 )

then Ff= ma2 = 2 x -2 = -4 N ( 1 mark )

(b) Between t = 0 s and t = 5 s, the acceleration a1 isa1= gradient = 10/5 = 2ms

-2 ( 1 mark )then F Ff= ma1

F 4 = 2 x 2 ( 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 (10)(5) = 200 J ( 1 mark )Between t = 5 s and t = 10 s,Work done = F x disp. = 4 x (10)(5) = 200 J ( 1 mark )Between t = 10 s and t = 15 s, F = 0 NWork done = F x disp. = 0 JTotal work done = 200+200+0 = 400 J ( 1 mark )

(ii)Work done by Ff= Ffx disp. =- 4 x (10)(5 +15) ( 1 mark )

= -400 J ( 1 mark )

10. (a)

i. Gravitational force F1 =( )( )

( )N

r

Gm 52210

23111

2

2

1015.6100.3

1011.91067.6

=

=

ii. Electrostatic force

F2 =( )

( )( )N

r

e 921012

219

2

0

2

1056.2100.31085.84

1060.1

4

=

=

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iii. 4252

9

1

2 1016.41015.6

1056.2=

=

F

F. This means that the electrostatic force is

( )421016.4 times more than the gravitational force until the value of the gravitationaforce can be neglected.

(b) i.2

21

r

MGMF = ;

F: gravitational attractive force between two objects,M1M2 : masses of the two objectsG : gravitational constantr: 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.

( )( )

kgM

mgR

GMm 2423

11

2106.02MEarthofmassThe;81.9

106400

1067.6; ==

=

iii. The weight of an object at a height h from the surface of the Earth is mg. This value is the same as thgravitational attractive force between the object and the Earth.

( )21

hR

GMmg+

=( )2

strengthfieldnalgravitatiothehR

GMg+

=

iv. v = gR2 = 310640081.92 = 1.12 X 10 4

11. (a)

Stationary waves Progressive waves

The profile of wave does notmove

The profile of the waves move in thedirection of propagation

No energy transferred alongthe wave

Energy transferred along the directionof wave propagation

Points in between two nodesare in the same phase.

Nearby points are not in the samephase.

Particles between successivenodes have different

amplitudes

Neighbouring particles in the mediumhave 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

propagation.[1],

A

PI = where P = Rate of energy transferred and A = area of surface SI unit : Wm-2 [1]

(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.

rI

1 [1]

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. 2aI [1]

Hence, the amplitude of the wave decreases as the distance of the wavefront from O increases.

(e)r

I1

2aI

ra

12

ra 2 = constant

[1]2

2

22

2

1

2

12

2

2

Aa

r

rAa

rara

=

=

=

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 magneti

field experiences a force of 1 newton.

(b) - the charged particle is stationary.

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

(c) (i)

(ii)

F

B

v

q

116

31

14

sm100.5

1011.9

106.4

=

=

=m

Fa

N106.4

104.3106.1104.8

14

7193

=

=

= BevF

[1]

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(iii)

(iv)

(d) (i)

=>=====>===>=m

eBrv

r

mvBe

r

mvBev

r

mvF

22

(ii) If they are electrons,

.103.5

1011.9

106.1)1050)(100.6(

111

31

1935

lightofspeedsm

v

>=

=

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.

Region of

magnetic field

vertically down

into the paper

Electron beam

Tangential to

the curve

mm9.22

106.4

)104.3)(1011.9(14

2731

2

=

=

=

r

mvF

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b) (i) (ii)

(iii)

c) (i)

(ii)

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c)

14.. (a) (i) Mass defect : The difference between the total mass of all free nucleons and the mass of thenucleus.

(ii) Activity is the rate of nuclear disintegration or the number of nucleidecaying 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

(b) H11 + C13

6 N13

7 + n1

0

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 thechange . (1)

(c ) U235

92 + n1

0 La148

57 + Br85

35 + 3 ( n1

0 )

(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 (1)

Energy released ; E = m 2c = (0.1795 x 1.66x 2710 )(3.00 x 810 ) 2 (1)

= 2.68 x 1110 J (1)

i

ii

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(iii) The energy produced by the reactor in 12 hours

E =Pt = 610 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 x20

100(1)

=2.16 x 1110 J (1)

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stpm trial 2009 phy q&a (n9)

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