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# Practice Questions : Laws of Motion JEE Notes | EduRev

## JEE : Practice Questions : Laws of Motion JEE Notes | EduRev

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1
PRACTICE SET
LAWS OF MOTION
CODE- 2009                   Time: 25 mins.                   Max. Marks. 60
Topics Covered: Application of Newton’s Laws of Motion in simple situations with Friction.
Level : Basic Conceptual Level

INSTRUCTIONS:   Problems (1-15) are Single Answer Correct Type, 4 marks each for correct option and -1
for every wrong attempt.

1. For the arrangement
shown in the fig. the
tension in the string is
[Given: tan
?1
(0.8) =
39
0
].
(a) 6N         (b) 6.4 N
(c) 0.4N       (d) zero
2. A body of mass 2 kg is at rest on a
horizontal table. The coefficient of friction
between the body and the table is 0.3. A
force of 5N is applied on the body. The
acceleration of the body is
(a) 0 ms
?2
(b) 2.5 ms
?2

(c) 5 ms
?2
(d) 7.5 ms
?2

3. In Q. 2, the force of friction is
(a) 5N        (b) 5.88 N
(c) 6N        (d) 20 N
4. The block A in fig weighs 100N. The
coefficient of static friction between the
block and the table is 0.25. The weight of
the block B is maximum for the system to
be in equilibrium. The value of T
1
is
A
45
0
T
2
T
2
T
1
T
1
B

(a) 0.25 N         (b) 25N
(c) 100N        (d) 10.25 N

5. Block A of
mass 2kg is
placed over a
block B of
mass 8kg.
The combination is placed on a rough
horizontal surface. If g = 10 ms
?2
,
coefficient of friction between B and floor =
0.5, coefficient of friction between B and
floor = 0.5, coefficient of friction between A
and B = 0.4 and a horizontal force of 10N is
applied on 8kg block, then the force of
friction between A and B is
(a) 100N  (b) 50N
(c) 40N  (d) None of these
6. A block of mass 1kg is at rest on a
horizontal table. The coefficient of static
friction between the block and the table is
0.5. The magnitude of the force acting
upwards at an angle of 60
0
from the
horizontal that will just start the block
moving is
(a) 5N   (b)
20
N
23 ?

(c)
20
N
23 ?
(d) 10 N
7. A box of mass m kg is placed on the rear
side of an open truck accelerating at 4 ms
?2
.
The coefficient of friction between the box
and the surface below it is 0.4. The net
acceleration of the box with respect to the
truck is zero.  The value of m is
(a) 4 kg     (b) 8kg
(c) 9.78 kg           (d) It could be any value

8kg
2kg A
B 10N
27.89
0
? = 0.8
m = 1kg
Page 2

1
PRACTICE SET
LAWS OF MOTION
CODE- 2009                   Time: 25 mins.                   Max. Marks. 60
Topics Covered: Application of Newton’s Laws of Motion in simple situations with Friction.
Level : Basic Conceptual Level

INSTRUCTIONS:   Problems (1-15) are Single Answer Correct Type, 4 marks each for correct option and -1
for every wrong attempt.

1. For the arrangement
shown in the fig. the
tension in the string is
[Given: tan
?1
(0.8) =
39
0
].
(a) 6N         (b) 6.4 N
(c) 0.4N       (d) zero
2. A body of mass 2 kg is at rest on a
horizontal table. The coefficient of friction
between the body and the table is 0.3. A
force of 5N is applied on the body. The
acceleration of the body is
(a) 0 ms
?2
(b) 2.5 ms
?2

(c) 5 ms
?2
(d) 7.5 ms
?2

3. In Q. 2, the force of friction is
(a) 5N        (b) 5.88 N
(c) 6N        (d) 20 N
4. The block A in fig weighs 100N. The
coefficient of static friction between the
block and the table is 0.25. The weight of
the block B is maximum for the system to
be in equilibrium. The value of T
1
is
A
45
0
T
2
T
2
T
1
T
1
B

(a) 0.25 N         (b) 25N
(c) 100N        (d) 10.25 N

5. Block A of
mass 2kg is
placed over a
block B of
mass 8kg.
The combination is placed on a rough
horizontal surface. If g = 10 ms
?2
,
coefficient of friction between B and floor =
0.5, coefficient of friction between B and
floor = 0.5, coefficient of friction between A
and B = 0.4 and a horizontal force of 10N is
applied on 8kg block, then the force of
friction between A and B is
(a) 100N  (b) 50N
(c) 40N  (d) None of these
6. A block of mass 1kg is at rest on a
horizontal table. The coefficient of static
friction between the block and the table is
0.5. The magnitude of the force acting
upwards at an angle of 60
0
from the
horizontal that will just start the block
moving is
(a) 5N   (b)
20
N
23 ?

(c)
20
N
23 ?
(d) 10 N
7. A box of mass m kg is placed on the rear
side of an open truck accelerating at 4 ms
?2
.
The coefficient of friction between the box
and the surface below it is 0.4. The net
acceleration of the box with respect to the
truck is zero.  The value of m is
(a) 4 kg     (b) 8kg
(c) 9.78 kg           (d) It could be any value

8kg
2kg A
B 10N
27.89
0
? = 0.8
m = 1kg

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2
PRACTICE SET
LAWS OF MOTION
8. Two masses A and B of
10 kg and 5 kg
respectively, are
connected with a string
passing over a
frictionless pulley fixed
at the corner of a table as shown in fig. the
coefficient of friction of A with the table is
0.2. the minimum mass of C that may be
placed on A to prevent it from moving is
(a) 15 kg  (b) 5 kg
(c) 10 kg  (d) 0 kg
9. A body of mass 8kg lies on a rough
horizontal table. It is observed that a certain
horizontal force gives the body an
acceleration of 4 ms
?2
. When this force is
doubled, the acceleration of the body is 16
ms
?2
. The coefficient of friction is
(a) 0.2           (b) 0.3
(c) 0.4         (d) 0.8
10. A 40 kg slab rests on a frictionless floor. A
10kg block rests on top of the slab. The
static coefficient of friction between the
block and the slab is 0.60 while the kinetic
coefficient of friction is 0.40. The 10 kg
block is acted upon by a horizontal force of
100N. The resulting acceleration of the slab
will be

40kg
10kg
No Friction
100N

(a) 1.5 m s
?2
(b) 2.0 ms
?2

(c) 10 ms
?2
(d) 1.0 ms
?2

11. A body of mass 40 kg resting on a rough
horizontal surface is subjected to a force P
which is just enough to start the motion of
the body. If ?
s
= 0.5 ?
k
= 0.4, g = 10 ms
?2

and the force P is continuously applied on
the body, then the acceleration of the body
is
(a) zero        (b) 1 ms
?2

(c) 2ms
?2
(d) 2.4 ms
?2

12. A block of mass m on
a rough horizontal
surface is acted upon
by tow forces as
shown in fig. For
equilibrium of block, the coefficient of
friction between block and surface is
(a)
12
2
F F sin
mg F cos
??
??
(b)
12
2
F cos F
mg F sin
??
??

(c)
12
2
F F cos
mg F sin
??
??
(d)
12
2
F sin F
mg F cos
??
??

For Problems (13-15)
Blocks A, B and C are placed in figure and
connected by ropes of negligible mass. Both A and
B weigh 25.0 N each and the coefficient of kinetic
friction between each block and the surface is 0.3.
Block C descends with constant velocity.
B
C
37° A

13. Find the tension in the rope connecting
blocks A and B.
(a) 9.0N  (b) 7.5N
(c) 25.0N  (d) 28.50N
14. What is the weight of block C?
(a) 9.0N  (b) 7.5N
(c) 25.0N  (d) 28.50N
15. If the rope connecting A and B were cut,
what would be the acceleration of C?
(a) 1.4m/s
2
(b) zero
(c) 3.6m/s
2
(d) none of these
C
A
B
m
F
2
F
1
?
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