INSTRUCTIONS A. General 1. This booklet is your Question Paper containing 57 questions. 2. The Question Paper CODE is printed on the right hand top corner of this page and on the back page of this booklet. 3. Each page of this question paper contains half page for rough work (except front and back page). No additional sheets will be provided for rough work. 4. Blank paper, clipboard, log tables, slide rules, calculators, cellular phones, pagers, and electronic gadgets in any form are not allowed to be carried inside the examination hall. 5. Fill in the boxes provided below on this page and also write your Name and Roll No. in the space provide on the back page of this booklet. 6. The answer sheet, a machine-readable Objective Response Sheet (ORS), is provided separately. 7. DO NOT TAMPER WITH/ MUTILATE THE ORS OR THE BOOKLET. 8. Do not open the seals of question-paper booklet before being instructed to do so by the invigilators. B. Filling the ORS : 9. Write your Roll No. in ink, in the box provided in the upper part of the ORS and darken the appropriate bubble UNDER each digit of your Roll No. with a good quality HB pencil. C. Question paper format : D. Marking scheme Read the instructions printed on the back page of this booklet. Name of the Candidate Roll Number I have read all the instructions and shall abide by them. -------------------------------- Signature of the Candidate -------------------------------- Signature of the Invigilator Please read the instructions carefully. You are allotted 5 minutes specifically for this purpose. Date : 12-04-2009 Duration : 3 Hours Max. Marks : 240 PAPER - 2 QUESTIONS & SOLUTIONS OF IIT-JEE 2009
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INSTRUCTIONSA. General1. This booklet is your Question Paper containing 57 questions.
2. The Question Paper CODE is printed on the right hand top corner of this page and onthe back page of this booklet.
3. Each page of this question paper contains half page for rough work (except front andback page). No additional sheets will be provided for rough work.
4. Blank paper, clipboard, log tables, slide rules, calculators, cellular phones, pagers, andelectronic gadgets in any form are not allowed to be carried inside the examination hall.
5. Fill in the boxes provided below on this page and also write your Name and Roll No. inthe space provide on the back page of this booklet.
6. The answer sheet, a machine-readable Objective Response Sheet (ORS), is providedseparately.
7. DO NOT TAMPER WITH/ MUTILATE THE ORS OR THE BOOKLET.
8. Do not open the seals of question-paper booklet before being instructed to do so by theinvigilators.
B. Filling the ORS :
9. Write your Roll No. in ink, in the box provided in the upper part of the ORS and darkenthe appropriate bubble UNDER each digit of your Roll No. with a good quality HB pencil.
C. Question paper format :
D. Marking schemeRead the instructions printed on the back page of this booklet.
Name of the Candidate
Roll Number
I have read all the instructions andshall abide by them.
-------------------------------- Signature of the Candidate
-------------------------------- Signature of the Invigilator
Please read the instructions carefully. You are allotted 5 minutes specifically for this purpose.
Date : 12-04-2009 Duration : 3 Hours Max. Marks : 240
PAPER - 2
QUESTIONS & SOLUTIONS OF IIT-JEE 2009
RESONANCE Page # 2
PART ICHEMISTRY
SECTION - IStraight Objective Type
This section contains 4 multiple choice questions. Each question has 4 choices (A), (B), (C) and (D)for its answer, out of which ONLY ONE is correct.
1. The correct stability order of the following resonance structures is :
(A) (I) > (II) > (IV) > (III) (B) (I) > (III) > (II) > (IV)
(C) (II) > (I) > (III) > (IV) (D) (III) > (I) > (IV) > (II)
This section contains 8 questions. The answer to each of the questions is a single digit integer, ranging from0 to 9. The appropriate bubbles below the respectively question numbers in the ORS have to be darkened.For example, if the correct answers to question number X, Y, Z and W (say) are 6, 0, 9 and 2, respectively,then the correct darkening of bubbles will like the following :
RESONANCE Page # 9
12. The total number of and particles emitted in the nuclear reaction U23892 Pb142
28 is
Ans. 8
Sol. U23892
Pb14228 + )He(6 4
2 + 2(�1
e0)
= 6, = 2Total = 8
13. The number of water molecule (s) directly bonded to the metal centre in CuSO4. 5H
2O is
Ans. 4
Sol.
14. The oxidation number of Mn in the product of alkaline oxidative fusion of MnO2 is
Ans. 6
Sol. 2MnO2 + 4KOH + O
2
fusion 2K
2MnO
4 + 2H
2O
Let the oxidation state of Mn in MnO4
2� is x.So x + 4 (�2) = �2 or x = 6
15. The Coordination number of Al in the crystalline state of AlCl3 is
Ans. 6
16. In a constant volume calorimeter, 3.5 g of a gas with molecular weight 28 was burnt in excess oxygen at298.0 K. The temperature of the calorimeter was found to increases from 298.0 K to 298.45 K due to thecombustion process. Given that the heat capacity of the calorimeter is 2.5 kJ K�1, the numerical value for theenthalpy of combustion of the gas in kJ mol�1 is
Ans. 9
Sol. n = 28
5.3
T = T2 � T
1 = 298.45 � 298
= 0.45
CV = 2.5 kJ k�1 = 2500 JK�1
CP = C
V + R = 2500 + 8.314
= 2508.314 JK�1
QP = C
PT = 1128.74 J
H = 28/5.374.1128
n
Qp 9030 J mol�1
= 9.030 KJ mol�1
= 9 KJ mol�1.
RESONANCE Page # 10
17. The total number of cyclic structural as well as stereo isomers possible for a compound with the molecularformula C
5H
10 is
Ans. 7
Sol.
18. The dissociation constant of a substituted benzoic acid at 25ºC is 1.0 × 10�4 . The pH of 0.01 M solution ofits sodium salt is
Ans. 8
Sol. Given Ka = 10�4
pKa = 4
C = 0.01 M
pH = 7 + 21
pKa +
21
log C
= 7 + 21
(4) + 21
(�2)
= 8 Ans.
19. At 400 K, the root mean square (rms) speed of a gas X (molecular weight = 40) is equal to the most probablespeed of gas Y at 60 K. The molecular weight of the gas Y is
Ans. MY = 4.
Sol. Vrms
= Vmp
XMRT3
= YM
RT2
40400R3
= YM60R2
MY = 4.
RESONANCE Page # 11
PART-II
MATHEMATICSSECTION - I
Single Correct Choice Type_____________________________________________________________________________
This section contains 4 multiple choice questions. Each question has 4 choices (A), (B), (C) and (D)for its answer, out of which ONLY ONE is correct.
20. The normal at a point P on the ellipse x2 + 4y2 = 16 meets the x-axis at Q. If M is the mid point of the linesegment PQ, then the locus of M intersects the latus rectum of the given ellipse at the points
(A)
72
,253
(B)
419
,253
(C)
71
,32 (D)
734
,32
Sol. (C)
16x2
+ 4y2
= 1
a = 4, b = 2equation of normal 4x sec � 2y cosec = 12
M
sin,
2cos7
= (h, k) (say)
h = 2
cos7 cos =
7h2
and k = sin
49h4 2
+ k2 = 1
locus 49x4 2
+ y2 = 1 ....(i)
for given ellipse e2 = 1 � 164
= 43
e = 23
x = ± 4 × 23
= ± 32 ....(ii)
solving (i) and (ii)
494
× 12 + y2 = 1
y2 = 1 � 4948
= 491
y = ± 71
required points
71
,32
RESONANCE Page # 12
21. The locus of the orthocentre of the triangle formed by the lines
(1 + p) x � py + p (1 + p) = 0, (1 + q) x � qy + q(1 + q) = 0, and y = 0, where p q, is
(A) a hyperbola (B) a parabola (C) an ellipse (D) a straight line
Sol. (D)
(1 + p) x � py + p (1 + p) = 0 ......(1)
(1 + q) x � qy + q(1 + q) = 0 ......(2)
on solving (1) and (2), we get C(pq, (1 + p) (1 + q))
equation of altitude CM passing through C and perpendicular to AB is x = pq .......(3)
slope of line (2) is =
qq1
slope of altitude BN (as shown in figure) is = q1q
equation of BN is y � 0 = q1q
(x + p)
y = )q1(q
(x + p) ....... (4)
Let orthocentre of triangle be H(h, k) which is the point of intersection of (3) and (4)
on solving (3) and (4), we get
x = pq and y = � pq h = pq and k = �pq
h + k = 0
locus of H(h, k) is x + y = 0
22. A line with positive direction cosines passes through the point P(2, �1, 2) and makes equal angles with the
coordinate axes. The line meets the plane 2x + y + z = 9 at point Q. The length of the line segment PQ
equals
(A) 1 (B) 2 (C) 3 (D) 2
Sol. (C)
= m = n = 3
1
2x + y + 2 = 9
equations of line are 3/1
2�x =
3/1
1y =
3/1
2�z
x � 2 = y +1 = z � 2 = r
Q (r + 2, r � 1, r + 2)
Q Lies on the plane 2x + y + z = 9
2(r + 2) + (r � 1) + (r + 2) = 9
4r + 5 = 9 r = 1
Q (3, 0, 3)
PQ = 111 = 3
RESONANCE Page # 13
23. If the sum of first n terms of an A.P. is cn2, then the sum of squares of these n terms is
31. Let f : R R be a continuous function which satisfies f(x) = x
0
dt)t(f . Then the value of f(n 5) is
Ans. 0
Sol. From given integral equation, f(0) = 0.Also differentiating the given integral equation w.r.t. xf(x) = f(x)
If f(x) 0 )x(f)x(f
= 1 f(x) = ec ex
f(0) = 0 ec = 0, a contradiction f(x) = 0 x R f(n 5) = 0
32. The centres of two circles C1 and C
2 each of unit radius are at a distance of 6 units from each other. Let P be
the mid point of the line segment joining the centres of C1 and C
2 and C be a circle touching circles C
1 and C
2
externally. If a common tangent to C1 and C passing through P is also a common tangent to C
2 and C, then
the radius of the circle C isAns. 8
Sol. (r + 1)2 = 2 + 9r2 + 8 = 2
r2 + 2r + 1 = r2 + 8 + 92r = 16r = 8
33. The smallest value of k, for which both the roots of the equation x2 � 8kx + 16(k2 � k + 1) = 0 are real, distinct
and have values at least 4, isAns. 2
Sol. (i) x2 � 8kx + 16(k2 � k + 1) = 0
D = 64 (k2 � (k2 � k + 1)) = 64 (k � 1) > 0
k > 1
(ii) � a2
b > 4
2k8
> 4 k > 1
(iii) f(4) 0
16 � 32k + 16 (k2 � k + 1) 0
k2 � 3k + 2 0
(k � 2) (k � 1) 0
k 1 or k 2
Hence k = 2
RESONANCE Page # 23
34. The maximum value of the function f(x) = 2x3 � 15x2 + 36x � 48 on the set A = {x |x2 + 20 9x} is
Ans. 7
Sol. A = {x |x2 + 20 9x} = {x |x [4, 5]}
Now, f(x) = 6(x2 � 5x + 6)
f(x) = 0 x = 2, 3
f(2) = �20, f(3) = �21, f(4) = �16, f(5) = 7
from graph, maximum of f(x) on set A is f(5) = 7
35. Let ABC and ABC be two non-congruent triangles with sides AB = 4, AC = AC = 22 and angle B= 30º. The
absolute value of the difference between the areas of these triangles is
Ans. 4
Sol. In ABC, by sine rule
Asina
= º30sin
22 =
Csin4
C = 45º, C = 135º
When C = 45º A = 180º � (45º + 30º) = 105º
When C = 135º A = 180º � (135º + 30º) = 15º
Area of ABC = 21
AB × AC sin A = 21
× 4 × 22 sin (105º) = 24 × 22
13
Area of ABC = 21
AB × AC sinA = 21
× 4 × 22 sin (15º) = 2 1�3
Difference of areas of triangles = | 2 13 � 2 1�3 | = 4
Aliter
AD = 2 , DC = 2
Difference of Areas of triangle ABC and ABC = Area of triangle ACC
= 21
AD × CC = 21
× 2 × 4 = 4
RESONANCE Page # 24
36. If the function f(x) = x3 + 2x
e and g(x) = f�1(x), then the value of g(1) is
Ans. 2Sol. g(f(x)) = x
g(f(x)) f(x) = 1 ........(i)if f(x) = 1 x = 0, f(0) = 1substitute x = 0 in (i), we get
g(1) = )0(f1
g(1) = 2 (f(x) = 3x2 + 21
ex/2 f(0) = 21
)
37. Let p(x) be a polynomial of degree 4 having extremum at x = 1, 2 and 0xlim
2x
)x(p1 = 2. Then the value of
p(2) isAns. 0
Sol. p(x) = ax4 + bx3 + cx2 + dx + e
p (x) = 4ax3 + 3bx2 + 2cx + d
p (1) = 4a + 3b + 2c + d = 0 .....(i)
p (2) = 32 a + 12 b + 4c + d = 0 .....(ii)
0xlim
2x
)x(p1 = 2
0xlim
2
234
x
edxx)1c(bxax = 2
c + 1 = 2, d = 0, e = 0
c = 1
Now equation (i) and (ii) are
4a + 3b = � 2 and 32 a + 12 b = � 4
a = 41
and b = � 1
38. Let (x, y, z) be points with integer coordinates satisfying the system of homogeneous equations :
3x � y � z = 0, �3x + z = 0, �3x + 2y + z = 0. Then the number of such points for which x2 + y2 + z2 100
is
Ans. 7
Sol. 3x � y � z = 0 .........(1)
�3x + 2y + z = 0 .........(2)�3x + z = 0 .........(3)
(1) + (2) y = 0So 3x = z
Now x2 + y2 + z2 100 x2 + (3x)2 + 0 100
10x2 100
x2 10
x = �3, �2, �1, 0, 1, 2, 3
So No.of such 7 points are possible
RESONANCE Page # 25
PART - IIIPHYSICSSECTION - I
Single Correct Choice Type
Thus section contains 4 multiple choice questions. Each question has 4 choices (A), (B), (C) and (D) for itsanswer, out which ONLY ONE is correct.
39. Photoelectric effect experiments are performed using three different metal plates p, q and r having work
functions p = 2.0 eV, q = 2.5 eV and r = 3.0 eV respectively. A light beam containing wavelengths of 550
nm, 450 nm and 350 nm with equal intensities illuminates each of the plates. The correct -V graph for the
experiment is [Take hc = 1240 eV nm]
(A) (B)
(C) (D)
Sol. (A)
eV25.2eV550
1240E nm5501
eV8.2eV450
1240E nm4502
eV5.3eV350
1240E nm3503
For metal r, only 3 is able to generate photoelectron.
For metal q, only and
are able to generate photoelectron.
For metal p, all wavelength are able to generate photoelectron.
Hence photoelectric current will be maximum for p and least for r.
RESONANCE Page # 26
40. A uniform rod of length L and mass M is pivoted at the centre. Its two ends are attached to two springs of
equal spring constants k. The springs are fixed to rigid supports as shown in the figure, and the rod is free to
oscillate in the horizontal plane. The rod is gently pushed through a small angle in one direction and
released. The frequency of oscillation is :
(A) Mk2
21
(B) Mk
21
(C) Mk6
21
(D) M
k2421
Sol. (C)
Torque about P = (kx) 2L
+ (kx) 2L
= kxL = k 2L2
For small angle , x = 2L
=
� 12
ML2
KL 22
MK6
=
= MK6
and f =
2 =
MK6
21
RESONANCE Page # 27
41. A piece of wire is bent in the shape of a parabola y = kx2 (y-axis vertical) with a bead of mass m on it. The
bead can slide on the wire without friction. It stays at the lowest point of the parabola when the wire is at rest.
The wire is now accelerated parallel to the x-axis with a constant acceleration a. The distance of the new
equilibrium position of the bead, where the bead can stay at rest with respect to the wire, from the y-axis is
(A) gka
(B) gk2a
(C) gka2
(D) gk4a
Sol. (B)
ma cos = mg cos (90 � )
tanga
ga
= dxdy
dxd
(kx2) = ga
x = gk2a
= D
42. The mass M shown in the figure oscillates in simple harmonic motion with amplitude A. The amplitude of the
point P is
M
k2k1
P
(A) 2
1
kAk
(B) 1
2
kAk
(C) 21
1
kkAk
(D) 21
2
kkAk
RESONANCE Page # 28
Sol. (D)
Extentions in springs are x1 and x2 then
k1x1 = k2x2
and x1 + x2 = A
x1 + 2
11
kxk
= AA x1 = 21
2
kkAk
SECTION - II
Multiple Correct Choice Type
This section contains 5 multiple choice questions. Each question has 4 choices (A), (B), (C) and (D) for its
answer, out of which ONE OR MORE is/are correct.
43. Under the influence of the Coulomb field of charge +Q, a charge �q is moving around it in an elliptical orbit.
Find out the correct statement(s).
(A) The angular momentum of the charge �q is constant
(B) The linear momentum of the charge �q is constant
(C) The angular velocity of the charge � q is constant
(D) The linear speed of the charge �q is constant
Sol. (A)
Torque about Q of charge �q is zero, so angular momentum charge �q is constant, but distance between
charges is changing, so force is changing, so speed and velocity are changing.
44. The figure shows the P-V plot of an ideal gas taken through a cycle ABCDA. The part ABC is a semi-circle
and CDA is half of an ellipse. Then,
(A) the process during the path A B is isothermal
(B) heat flows out of the gas during the path B C D
(C) work done during the path A B C is zero
(D) positive work is done by the gas in the cycle ABCDA
RESONANCE Page # 29
Sol. (B, D)
(A) process is not isothermal
(B) volume decreases and temperature decreases
U = negative
W = negative
so Q = negative
(C) Work done in process A B C is positive
(D) Cycle is clockwise, so work done by the gas is positive.
45. A sphere is rolling without slipping on a fixed horizontal plane surface. In the figure, A is the point of contact,
B is the centre of the sphere and C is its topmost point. Then,
(A) AC VV
= CB VV2
(B) BC VV
= AB VV
(C) AC VV
= CB VV2
(D) AC VV
= BV4
Sol. (B, C)
)i�(R)i�(VVA
; i�VVB
; i�Ri�VVC
i�R2VV AC
2 )]i�(R)i�(V)i�(V[2VV CB
= �2R( i� )
Hence AC VV
= )VV(2 CB
so |VV| AC
= |)VV(2| CB
BC VV
= R( i� )
AB VV
= R( i� )
ABBC VVVV
Hence )i�(R2VV AC
ABBC VVVV
; BV4
= 4V( i� ) = 4R ( i� )
Hence )V(2VV BAC
RESONANCE Page # 30
46. A student performed the experiment to measure the speed of sound in air using resonance air-column
method. Two resonances in the air-column were obtained by lowering the water level. The resonance with the
shorter air-column is the first resonance and that with the longer air-column is the second resonance. Then,
(A) the intensity of the sound heard at the first resonance was more than that at the second resonance
(B) the prongs of the tuning fork were kept in a horizontal plane above the resonance tube
(C) the amplitude of vibration of the ends of the prongs is typically around 1 cm
(D) the length of the air-column at the first resonance was somewhat shorter than 1/4th of the wavelength of
the sound in air.
Sol. (A, D)
(A) The intensity of second decreases with increases of order. The intensity of
sound is maximum for first resonance.
(B) The prongs vibrate in vertical plane.
(C) The prongs does not vibrate in amplitude of that order.
(D) Consider end correction, the length of air column is slightly less than /4
So ans are (A) and (D)
47. Two metallic rings A and B, identical in shape and size but having different resistivities A and B, are kept on
top of two identical solenoids as shown in the figure. When current is switched on in both the solenoids in
identical manner, the rings A and B jump to heights hA and hB, respectively, with hA > hB. The possible
relation(s) between their resistivities and their masses mA and mB is(are)
A B
(A) A > B and mA = mB (B) A < B and mA = mB
(C) A > B and mA > mB (D) A < B and mA < mB
Sol. (B, D)
The horizotanl component of magnetic field due to
solenoid will exert force on ring in vertical direction
F = BHi (2r)
Ft = MV
i =
A)r2()t/(
BH i (2r) t = MV
V = MK
MABH
RESONANCE Page # 31
h = 22
22
M
K
g2
V
hA > hB
2B
2B
2
2A
2A
2
M
K
M
K
BMB > AMA
Using this we get
Answer (B) and (D)
Section�III
Matrix � Match TypeThis section contains 2 questions. Each question contains statements given in two columns, which have to
be matched. The statements in Column�I are labelled A,B,C and D, while the statements in Column-II are
labelled p,q,r,s and t. Any given statement in Column-I can have correct matching with ONE OR MORE
statement(s) in Column-II. The appropriate bubbles corresponding to the answers to these questions have
to be darkened as illustrated in the following examples :
If the correct matches A�p,s and t; B�q and r; C�p and q ; and D�s and t; then the correct darkening of
bubbles will look like the following.
p q r sp q r sp q r sp q r s
ABCD
p q r s
t
t
ttt
48. Column I shows four situations of standard Young�s double slit arrangement with the screen placed far away
from the slits S1 and S
2 . In each of these cases S
1P
0 = S
2P
0 , S
1P
1 � S
2P
1 =/4 and S
1P
2 � S
2P
2 = /3, where
is the wavelength of the light used. In the cases B,C and D, a transparent sheet of refractive index and
thickness t is pasted on slit S2. The thicknesses of the sheets are different in different cases. The phase
difference between the light waves reaching a point P on the screen from the two slits is denoted by (P) and
the intensity by (P). Match each situation given in Column-I with the statement(s) in Column-II valid for that
situation.
RESONANCE Page # 32
Column�I Column�II
(A) (p) (P0) = 0
(B) ( � 1)t = /4 (q) (P1) = 0
(C) ( � 1)t = /2 (r) (P1) = 0
(D) ( � 1)t = 3/4 (s) (P0) > (P
1)
Ans. (A) p, s; (B) q; (C) t ; (D) r, s, t
(t) (P2) > (P
1)
Sol. (A) (P1) =
1 +
2 + 2 21 cos
42
= 0 +
0 + 2
0 .
2
1 = (2 + 2 )
0
(P2) =
1 +
2 + 2
0 .
2
1 = 2 21 . cos
32
= 0 +
0 + 2
0 .
21
= 0
(P1) > (P
2)
(B) (P0) = ( � 1)t .
2 =
22
.4
(P1) = 0
2.
4t)1(
RESONANCE Page # 33
(P2) = 6
2.
3t)1(
(P0) =
1 +
2 + 2 21 . cos (P
0)
= 0 +
0 + 2
0 . cos
2
=20
(P0) = 4
0
(P2) =
0 +
0 + 2
0 cos
6
= (2 + 3 )0
(C). (P0) = ( � 1)t .
2 =
2.
2
(P1) = 2
24
2.t)1(
(P2) = 6
2.
3t)1(
(P0) = 3
26
2.
32
(D) (P0) =
232
43
(P1) = 0
(P2) > 0, (P
0) > 0
49. Column II gives certain systems undergoing a process. Column I suggests changes in some of the
parameters related to the system. Match the statements in Column-I to the appropriate process(es) from
Column II.
Column�I Column�II
(A) The energy of the system is increased. (p) System: A capacitor, initially uncharged
Process: It is connected to a battery.
(B) Mechanical energy is provided to the system, (q) System: A gas in an adiabatic container fitted with
which is converted into energy of random motion an adiabatic piston
of its parts Process: The gas is compressed by pushing the
piston
(C) Internal energy of the system is converted (r) System: A gas in a rigid container
into its mechanical energy Process: The gas gets cooled due to colder
atmosphere surrounding it
RESONANCE Page # 34
(D) Mass of the system is decreased (s) System: A heavy nucleus, initially at rest
Process: The nucleus fissions into two fragments of
nearly equal masses and some neutrons are emitted
(t) System: A resistive wire loop
Process: The loop is placed in a time varying
magnetic field perpendicular to its plane
Ans. (A) p, q, t; (B) q, t (C) s, (D) s
Sol .
(A) (p) : Capacitor is charged, hence its energy is increased
(q) : The temperature is increased, hence its energy is increased or as the external positive work is
done, hence energy increases
(r) : The temperature decreases, its energy is decreased
(s) : All natural process, energy of the system decreases
(t) : The current is poroduced. Hence energy of the system increases
(B) (p), (r), (s) no mechanical energy is provided to the system
(q) the mechanical energy is provided which increases the temperature and hence random motion of
molecules
(t) Mechanical work is done to change the magnetic field, which increases the mechancal energy of
electron and these electrons strike with stationary positive charge and energy is converted in random
motion.
(C) (s) Internal binding energy is converted into mechanical energy
(D) (s) Mass changes only in nuclear process.
SECTION�IV
Integer Answer TypeThis section contains 8 questions. The answer to each of the question is a single-digit integer, ranging from
0 to 9. The appropriate bubbles below the respective question numbers in the ORS have to be darkened. For
example, if the correct answers to question numbers X,Y,Z and W (say) are 6,0,9 and 2, respectively, then
the correct darkening of bubbles will look like the following :
RESONANCE Page # 35
50. A steady current goes through a wire loop PQR having shape of a right angle triangle with PQ = 3x, PR = 4x
and QR = 5x. If the magnitude of the magnetic field at P due to this loop is
x48k 0
, find the value of k.
Sol. B =
5x12
4
i0 (sin 37º + sin 53º)
B = x48i0
53
54
5
B = 7
x48i0
K = 7 Ans. 7
51. A light inextensible string that goes over a smooth fixed pulley as shown in the figure connects two blocks of
masses 0.36 kg and 0.72 kg. Taking g = 10 m/s2, find the work done (in joules) by the string on the block of
mass 0.36 kg during the first second after the system is released from rest.
Sol. T = gmmmm2
21
21
=
36.072.036.072.02
× 10
T = 4.8 N
RESONANCE Page # 36
a = gmmmm
21
21
=
3g
s = 2at21
= 21
3g
(1)2 = 6
10
Work done by T = (T) (S)
= (4.8) × 6
10 = 8J
Ans. 8
52. A solid sphere of radius R has a charge Q distributed in its volume with a charge density = kra, where k and
a are constants and r is the distance from its centre. If the electric field at r = 2R
is 81
times that at r = R, find
the value of a.
Sol.
Total charge Q = )R(3a
k4)drr4()Kr(Vd 3a
Rr
0r
2a
Q´ =
3a2/Rr
0r
2a
2
R
3a
k4)drr4()Kr(Vd
According to question
041
2)2/R(
´Q =
20 R
Q4
181
Putting the value of Q and Q´ get
a = 2 Ans. 2
53. A metal rod AB of length 10 x has its one end A in ice at 0ºC and the other end B in water at 100ºC. If a point
P on the rod is maintained at 400ºC, then it is found that equal amounts of water and ice evaporate and melt
per unit time. The latent heat of evaporation of water is 540 cal/g and latent heat of melting of ice is 80 cal/g.
If the point P is at a distance of x from the ice end A, find the value of . [ Neglect any heat loss to the
surrounding ]
Sol.
i1 = )kA/x(
0400
,
i2 = kA/x)10(
100400
RESONANCE Page # 37
v
f
v
f
2
1
LL
Ldtdm
Ldtdm
ii
54080
x)10/(300x/400
= 9 Ans. 9
54. Two soap bubbles A and B are kept in a closed chamber where the air is maintained at pressure 8 N/m2. The
radii of bubbles A and B are 2cm and 4cm, respectively. Surface tension of the soap-water used to make
bubbles is 0.04 N/m. Find the ratio nB/n
A, where n
A and n
B are the number of moles of air in bubbles A and B,
respectively. [Neglect the effect of gravity.]
Sol.
PA = P
0 +
ArT4
PA = 8 +
02.004.04
PA = 16 N/m2
PB = P
0 +
BrT4
= 8 + 04.0
04.04
PB = 12 N/m2
for bubble A, PV = nRT
(16) 34 (0.02)3 = n
A RT ....(1)
for bubble B
(12)
3)04.0(
34
= nBRT ....(2)
dividing eqn (i) and (2)
61
nn
B
A ; 6nn
A
B Ans. 6
55. A 20cm long string, having a mass of 1.0 g, is fixed at both the ends. The tension in the string is 0.5 N. The
string is set into vibrations using an external vibrator of frequency 100 Hz. Find the separation (in cm)
between the successive nodes on the string.
Sol.
v =
T =
2.0/10
5.03 = 10 m/sec.
v = f
10 = (100) = 0.1 m = 10 cm
distance between two successive nodes = 2
= 5 cm
Ans. 5
RESONANCE Page # 38
56. Three objects A,B and C are kept in a straight line on a frictionless horizontal surface. These have masses
m, 2m and m, respectively. The object A moves towards B with a speed 9 m/s and makes an elastic collision
with it. Thereafter, B makes completely inelastic collision with C. All motions occur on the same straight line.
Find the final speed (in m/s) of the object C.
Sol.
from momentum conservation :
9m = (2m) V1 � (m)V
2
9 = 2V1 � V
2..... (1)
e = 19
VV 21
......(2)
from eqn(1) and eqn(2) V1 = 6 m/sec.
for second collision between second block and third block :
(2m) 6 + m(0) = (2m + m) VC
VC = 4 m/sec.
Ans. 4
57. A cylindrical vessel of height 500 mm has an orifice (small hole) at its bottom. The orifice is initially closed
and water is filled in it up to height H. Now the top is completely sealed with a cap and the orifice at the
bottom is opened. Some water comes out from the orifice and the water level in the vessel becomes steady
with height of water column being 200 mm. Find the fall in height (in mm) of water level due to opening of the
orifice.
[Take atmospheric pressure = 1.0 × 105 N/m2 , density of water = 1000 kg/m3 and g = 10 m/s2. Neglect any
effect of surface tension]
Sol.
P0 = atmospheric pressure
P + 200 × 10�3 × 1000 × 10 = P0
....(1)
P = mm300mm)H500(P0
....(2)
RESONANCE Page # 39
from (1) and (2)
300)H500(P0
+ 2000 = P0
300)H500(105
+ 2000 = 105
5 × 107 � H × 105 + 6 = 300
H = 206 mm
fall in height = 6 mm
Ans. 6
C. Question paper format :
10. The question paper consists of 3 parts (Part I : Chemistry, Part II : Mathematics,Part-III : Physics). Each part has 4 sections.
11. Section I contains 4 multiple choice questions. Each question has 4 choices (A), (B), (C) and(D) for its answer, out of which only one is correct.
12. Section II contains 5 multiple choice questions. Each question has 4 choices (A), (B), (C)
and (D) for its answer, out of which one or more is/are correct.
13. Section III contains 2 questions Each question has four statements (A, B, C and D) given inColumn I and five statements (p, q, r, s and t) in Column II. Any given statement in Column Ican have correct matching with one or more statement(s) given in Column II. For example, iffor a given question, statement B matches with the statements given in q and r, then for thatparticular question, against statement B, darken the bubbles corresponding to q and r in theORS.
14. Section IV contains 8 questions. The answer to each of the questions is a single-digit integer,ranging from 0 to 9. The answer will have to be appropriately bubbled in the ORS as per theinstructions given at the beginning of the section.
Fill your Answer as is given in the following example.
Example : If the correct answers to question numbers X, Y, Z and W (say) are 6,0,9 and 2,
respectively, then the correct darkening of bubbles will look like the following :
D. Marking Scheme :
16. For each question in Section I , you will be awarded 3 marks if you darken the bubblecorresponding to the correct answer and zero mark if no bubble is darkened. In all case ofbubbling of incorrect answer, minus one (�1) mark will be awarded.
17. For each question in Section II , you will be awarded 4 marks if you darken the bubble(s)corresponding to the correct choice(s) for the answer and zero mark if no bubbled is darkened.In all other cases, minus one (�1) mark will be awarded.
18. For each question in Section III, you will be awarded 2 marks for each row in which you
have darkened the bubble(s) corresponding to the correct answer. Thus, each question in this
section carries a maximum of 8 marks. There is no negative marking for incorrect answer(s)
for this this section.
19. For each question in Section IV, you will be awarded 4 marks if you darken the bubblecorresponding to the correct answer, and zero mark if no bubble is darkened. In all other cases,minus one (�1) mark will be awarded.