Practice Questions : Laws of Motion JEE Notes | EduRev

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

 Page 1


 
 
 
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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