PG Brainstormer - 6c (Mechanics) 635453980676456802
PG Brainstormer - 6c (Mechanics) 635453980676456802
PG Brainstormer - 6c (Mechanics) 635453980676456802
PG Brainstormer - 6 C
KINEMATICS, NLM, FRICTION, WORK, ENERGY, POWER & MOMENTUM CONSERVATION
Time Allowed
Maximum Marks
60 Min
45
Instruction : Each question from 1 to 15 is of 3 Marks and there is a negative marking of -1 Mark.
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In this section 5 Paragraphs are given each with 3 questions. Each question has four choices (A), (B), (C) and (D) out of which
ONLY ONE is correct. Marking Scheme - +3 for RIGHT answer and -1 for WRONG answer.
# Comprehension-1:
Three identical uniform blocks of mass m each and length L are placed on a smooth fixed horizontal surface as
shown. There is friction between A and B while there is no friction between A and C. At the instant shown, that is at
t = 0; the block A has horizontal velocity of magnitude u towards right, whereas speed of B and C is zero. At the
instant block A has covered a distance L relative to block B velocity of all blocks are same.
L
A
B
2.
3.
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1.
2u
3
1 u2
3 gL
(B)
1 u2
2 gL
(C)
2 u2
3 gL
# Comprehension-2:
Two cars A and B start racing at the same time on a flat race track which consists of
two straight sections each of length 100 and one circular section as in fig. The
rule of the race is that each car must travel at constant speed at all times without
ever skidding.
If A = 0.1, B = 0.2 (A is coefficient of friction on track A and B is the coefficient
of friction on track B) then :
(A) Car A completes its journey before car B.
(B) Both cars complete their journey in same time
(C) Speed of car B is greater than that of car A.
(D) Speed of Car A is greater than that of Car B.
PH
4.
(D)
(D)
1 u2
8 gL
rB
rA
rA = 100 m
rB = 200 m
L = 100
BA
5.
If speed of car A is 108 kmph and speed of car B is 180 kmph, and both tracks are equally rough :
(A) Car A completes its journey before car B
(B) Both cars complete their journey in same time
(C) Speed of car A is greater than that of car B
(D) Car B completes its journey before car A.
6.
If VB = 96 kmph, the minimum value of A so that car A can complete its journey before car B is :
45
40
45
(A)
(B)
(C)
(D) None of these
128
100
64
PG Brainstormer - 6C
# Comprehension-3:
Two blocks of mass m1 = 10 kg and m2 = 20 kg are placed on a fixed inclined surface making an angle = 37 with
horizontal. One end of a light spring of spring constant K = 100 N/m is free and other end is connected to a support
S rigidly fixed to inclined surface. The coefficient of friction between block of mass m1 and inclined plane is 1 = 0.5
and that between block of mass m2 and inclined plane is 2 = 1. At time t = 0 both blocks are released at rest from
shown position. (Take g = 10 m/s2)
L=
1
K=
00 N
1. 4
8m
m1
m2
/m
=37
At the instant the speed of block of mass m1 is maximum, the compression in the spring is :
(A) 5 cm
(B) 10 cm
(C) 20 cm
(D) 60 cm
8.
At the instant speed of block of mass m1 is maximum, the speed of block of mass m2 is :
2
4
(A) Zero
(B) 2 m/s
(C) m/s
(D) m/s
3
3
9.
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7.
(D) 40 N
# Comprehension-4:
A horizontal massless string has its left end hinged to the fixed incline plane, while its
right end is tied to the top of a uniform cylinder of mass 'm' which in turn is at rest on the
fixed inclined plane of inclination 30 as shown. The coefficient of friction between the
cylinder and inclined plane, is sufficient to keep the cylinder at rest.
11.
12.
The magnitude of normal reaction exerted by the inclined plane on the cylinder is :
3 mg
(A) mg
(B)
(C) 2 mg
2
YS
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10.
hinge
(D)
mg
2
(D)
(C) 2 : 1
(D)
(C)
5 mg
4
mg
2 3
1
2 3
(B) 2 : 3
1
2 3
PH
# Comprehension-5:
A ball is hanging vertically by a light inextensible string of length L from fixed point O.
The ball of mass m is given a speed u at the lowest position such that it completes a
vertical circle with centre at O as shown. Let AB be a diameter of circular path of ball
making an angle with vertical as shown. (g is acceleration due to gravity).
14.
(A) 2 g sin
15.
30
13.
string
(B) g 12cos 2 4
(C) 4 g cos
Let KA and KB be kinetic energy of ball when it is at A and B respectively, then KA KB is equal to :
(A) mgL cos
(B) 2mgL cos
(C) 4mgL cos
(D) None of these
*
PG Brainstormer - 6C
PG Brainstormer - 6 C
KINEMATICS, NLM, FRICTION, WORK, ENERGY, POWER & MOMENTUM CONSERVATION
60 Min
45
GA
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Time Allowed
Maximum Marks
YS
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12
13
14
PH
15
PG Brainstormer - 6C
PG Brainstormer - 6 C
KINEMATICS, NLM, FRICTION, WORK, ENERGY, POWER & MOMENTUM CONSERVATION
Time Allowed
Maximum Marks
60 Min
45
ANSWER KEY
3. (A)
12. (A)
4. (C)
13. (A)
5. (D)
14. (B)
*
7.
(C)
8.
(A)
9.
(A)
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S
6. (B)
15. (B)
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2. (A)
11. (D)
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1. (B)
10. (A)