1. Xtra Edge February 2012 - Career Point

(A) potential energy (PE) increases but kinetic energy
(KE) decreases.
(B) PE decreases but KE increases.
(C) PE remains constant but KE increases.
(D) PE decreases but KE remains constant
8. A L shaped rod whose one rod is horizontal and other
is vertical is rotating about a vertical axis as shown
with angular speed ω. The sleeve shown in figure has
mass m and friction coefficient between rod and
sleeve is µ. The minimum angular speed ω for which
sleeve cannot sleep on rod is –
(A)
(C)
ω =
ω =
µ l
ω
l
m
g (B)
sleeve
ω =
µ g
l
l
(D) None of these
µ g
9. Four particles of equal mass M move along a circle of
radius R under the action of their mutual gravitational
attraction. The speed of each particle is -
GM
(A)
R
(B)
⎡
⎢2
⎣
GM ⎤
2
R
⎥
⎦
⎡GM
⎤
(C) ⎢ ( 2 2 + 1)
⎥
⎣ R ⎦
(D)
⎡GM
⎛ ⎞⎤
⎢ ⎜
2 2 + 1
⎟⎥
⎢
⎜ ⎟
⎣
R ⎝ 4 ⎠⎥⎦
This section contains 4 questions numbered 10 to 13,
(Reason and Assertion type question). Each question
contains Assertion (A) and Reason (R). Each question
has 4 choices (A), (B), (C) and (D) out of which ONLY
ONE is correct. Mark your response in OMR sheet
against the question number of that question. +3 marks
will be given for each correct answer and – 1 mark for
each wrong answer.
The following questions given below consist of an
"Assertion" (A) and "Reason" (R) Type questions. Use
the following Key to choose the appropriate answer.
(A) If both (A) and (R) are true, and (R) is the correct
explanation of (A).
(B) If both (A) and (R) are true but (R) is not the
correct explanation of (A).
(C) If (A) is true but (R) is false.
(D) If (A) is false but (R) is true.
10. Assertion (A) : A string of length 28 cm, fixed at one
end vibrates in its 3 rd overtone. Wave motion will not
be disturbed by holding the string at a distance 8 cm
from fixed end.
Reason (R) : Position of nodes in the above string
will at distance 4 cm, 8 cm, …. from fixed end.
11. Assertion (A) : Two tube of same length but
different diameter vibrating in same harmonic.
Frequency of tube having smaller diameter will be
more.
Reason (R) : End-correction is less in tube of smaller
diameter.
12. Assertion (A) : When an observer moves towards
stationary source frequency heard by observer is
more than that frequency emitted by source.
Reason (R) : Wavelength of sound wave received by
observer becomes smaller.
13. Assertion (A) : At height h from ground and at depth
h below ground, where h is approximately equal to
0.62 R, the value of g acceleration due to gravity is
same.
Reason (R) : Value of g decreases both sides, in
going up and down.
This section contains 2 paragraphs; each has 3 multiple
choice questions. (Questions 14 to 19) Each question
has 4 choices (A), (B), (C) and (D) out of which ONLY
ONE is correct. Mark your response in OMR sheet
against the question number of that question. +4 marks
will be given for each correct answer and – 1 mark for
each wrong answer.
Passage # 1 (Ques. 14 to 16)
A vertical cylindrical tube has its lower end closed.
There is small opening in the bottom of the tube by
which level of water in tube can be adjusted. Length
of tube is 50 cm. Velocity of sound in air and water
is 320 m/s and 1440 m/s respectively. Water is filled
in tube upto height 30 cm.
14. Minimum frequency with which tube can resonate is-
(A) 300 Hz (B) 320 Hz
(C) 400 Hz (D) 450 Hz
15. Minimum frequency so that standing waves can be
formed both in air and liquid column -
(A) 400 Hz (B) 800 Hz
(C) 640 Hz (D) 900 Hz
16. Air column in tube is resonating with a tuning fork at
its lowest possible frequency. Water level is lowered
slowly. Minimum distance by which water level has
to be lowered so that intensity of sound become
maximum is -
(A) 10 cm (B) 20 cm
(C) 40 cm (D) 50 cm
Passage # 2 (Ques. 17 to 19)
A wire of length 1 m is clamped horizontally between
two rigid support.
17. Wire is plucked at a distance 30 cm from one end.
Lowest harmonic in which wire can resonate is -
(A) 3rd (B) 4th (C) 5th (D) 10th
XtraEdge for IIT-JEE 61 FEBRUARY 2012