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IIT-JEE2006-PH-1
FIITJEE
Solutions to IITJEE–2006
P
P
h
h
y
y
s
s
i
i
c
c
s
s
Time: 2 hours
Note:
The marking Scheme is (+3,
−
1) for question numbers 1 to 12 , (+5,
1) for question numbers 13 to 20,
(+5,
2) for question numbers 21 to 32 and (+6, 0) for question numbers 33 to 40.
1
Given,
R
1
= 1
Ω
C
1
= 2
µ
F
R
2
= 2
Ω
C
2
= 4
µ
F
C
1
C
2
R
1
R
2
V
(I)
C
2
C
1
R
1
R
2
V
C
2
C
1
R
2
R
V
(II)
(III)
The time constants (in
µ
S) for the circuits I, II, III are respectively
(A) 18, 8/9, 4
(B) 18, 4, 8/9
(C) 4, 8/9, 18
(D) 8/9, 18, 4
Sol.
(D)
τ
1
= 8/9
µ
S
τ
2
= 18
µ
S
τ
3
= 4
µ
S
2.
Two blocks A and B of masses 2m and m, respectively, are connected by
a massless and inextensible string.
The whole system is suspended by a
massless spring as shown in the figure. The magnitudes of acceleration
of A and B, immediately after the string is cut, are respectively
(A) g,
g/2
(B) g/2, g
(C) g , g
(D) g/2, g/2
A
2m
B
m
Sol.
(B)
a
A
= g/2
a
B
= g
3 mg
2 mg
A
B
mg
3.
A point object is placed at a distance of 20 cm from a thin plano-convex lens of focal
length 15 cm, if the plane surface is silvered. The image will form at
(A)
60 cm left of AB
(B) 30 cm left of AB
(C) 12 cm left of AB
(D) 60 cm right of AB
Sol.
(C)
−
121
1
5
F
Ff
2
=+⇒=
−
∞
A
15 cm
20 cm
L
O
A
B
211
15
v
20
−=−
⇒
v =
−
12 cm
i.e.12 cm left of AB