Practice Test - Circular Motion (BMSAP) - JEE PDF Download

 Page 1


 
 
 
1 
PRACTICE SET 
CIRCULAR MOTION 
CODE- 2017                   Time: 25 mins.                   Max. Marks. 60  
Topics Covered: Application of Circular Motion in simple situations 
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.  A ball of mass 0.1 kg is whirled in a horizontal 
circle of radius 1 m by means of a string at an 
initial speed of 10 r.p.m.  Keeping the radius 
constant, the tension in the string is reduced to 
one quarter of its initial value. The new speed is
  
(a) 5 r.p.m.   (b) 10 r.p.m.  
(c) 20 r.p.m.  (d) 14 r.p.m. 
2. Three identical particles are joined together by a 
thread as shown in figure.  All the three particles 
are moving in a horizontal plane. If the velocity 
of the outermost particle is v
0
, then the ratio of 
tensions in the three sections of the string is  
 
(a) 3 : 5 : 7   (b) 3 : 4 : 5  
(c) 7 : 11 : 6  (d) 3 : 5 : 6 
3. A stone of mass 1 kg tied to the end of a string of 
length 1 m, is whirled in a horizontal circle with a 
uniform angular velocity of 2 rad/s. The tension 
of the string is (in N)     
(a) 2    (b) 
3
1
  
(c) 4   (d) 
4
1
 
4. A cord can bear a maximum force of 100 N 
without breaking. A body of mass 1 kg tied to 
one end of a cord of length 1 m is revolved in a 
horizontal plane. What is the maximum linear 
speed of the body so that the cord does not break   
(a) 10 m/s   (b) 20 m/s   
(c) 25 m/s   (d) 30 m/s  
5. A mass is supported on a frictionless horizontal 
surface. It is attached to a string and rotates about 
a fixed centre at an angular velocity ?
0
. If the 
length of the string and angular velocity are 
doubled, the tension in the string which was 
initially T
0
 is now      
(a) T
0
   (b) T
0
/2  
(c) 4T
0
   (d) 8T
0
  
6. A stone is rotated steadily in a horizontal circle 
with a period T by a string of length l. If the 
tension in the string is kept constant and l 
increases by 1%, what is the percentage change 
in T  
(a) 1%   (b) 0.5%  
(c) 2%   (d) 0.25% 
7. If mass speed and radius of rotation of a body 
moving in a circular path are all increased by 
50%, the necessary force required to maintain the 
body moving in the circular path will have to be 
increased by  
(a) 225%   (b) 125%  
(c) 150%   (d) 100% 
 
l l l 
O A B C 
 
Page 2


 
 
 
1 
PRACTICE SET 
CIRCULAR MOTION 
CODE- 2017                   Time: 25 mins.                   Max. Marks. 60  
Topics Covered: Application of Circular Motion in simple situations 
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.  A ball of mass 0.1 kg is whirled in a horizontal 
circle of radius 1 m by means of a string at an 
initial speed of 10 r.p.m.  Keeping the radius 
constant, the tension in the string is reduced to 
one quarter of its initial value. The new speed is
  
(a) 5 r.p.m.   (b) 10 r.p.m.  
(c) 20 r.p.m.  (d) 14 r.p.m. 
2. Three identical particles are joined together by a 
thread as shown in figure.  All the three particles 
are moving in a horizontal plane. If the velocity 
of the outermost particle is v
0
, then the ratio of 
tensions in the three sections of the string is  
 
(a) 3 : 5 : 7   (b) 3 : 4 : 5  
(c) 7 : 11 : 6  (d) 3 : 5 : 6 
3. A stone of mass 1 kg tied to the end of a string of 
length 1 m, is whirled in a horizontal circle with a 
uniform angular velocity of 2 rad/s. The tension 
of the string is (in N)     
(a) 2    (b) 
3
1
  
(c) 4   (d) 
4
1
 
4. A cord can bear a maximum force of 100 N 
without breaking. A body of mass 1 kg tied to 
one end of a cord of length 1 m is revolved in a 
horizontal plane. What is the maximum linear 
speed of the body so that the cord does not break   
(a) 10 m/s   (b) 20 m/s   
(c) 25 m/s   (d) 30 m/s  
5. A mass is supported on a frictionless horizontal 
surface. It is attached to a string and rotates about 
a fixed centre at an angular velocity ?
0
. If the 
length of the string and angular velocity are 
doubled, the tension in the string which was 
initially T
0
 is now      
(a) T
0
   (b) T
0
/2  
(c) 4T
0
   (d) 8T
0
  
6. A stone is rotated steadily in a horizontal circle 
with a period T by a string of length l. If the 
tension in the string is kept constant and l 
increases by 1%, what is the percentage change 
in T  
(a) 1%   (b) 0.5%  
(c) 2%   (d) 0.25% 
7. If mass speed and radius of rotation of a body 
moving in a circular path are all increased by 
50%, the necessary force required to maintain the 
body moving in the circular path will have to be 
increased by  
(a) 225%   (b) 125%  
(c) 150%   (d) 100% 
 
l l l 
O A B C 
 
 
 
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2 
PRACTICE SET 
CIRCULAR MOTION 
8. Two masses m and M are connected by a light 
string that passes through a smooth hole O at the 
centre of a table. Mass m lies on the table and M 
hangs vertically. m is moved round in a 
horizontal circle with O as the centre. If l is the 
length of the string from O to m then the 
frequency with which m should revolve so that 
M remains stationary is  
 
(a) 
l m
Mg
? 2
1
  (b) 
l m
Mg
?
1
  
(c) 
Mg
l m
? 2
1
  (d) 
Mg
l m
?
1
 
9.  A particle of mass M moves with constant speed 
along a circular path of radius r under the action 
of a force F.  Its speed is   
(a) 
m
F r
    (b) 
r
F
  
(c) r m F   (d) 
r m
F
 
10. A motor cycle driver doubles its velocity when he 
is having a turn. The force exerted outwardly will 
be 
(a) Double   (b) Half  
(c) 4 times   (d) 
4
1
 times 
11. A body is performing circular motion. An 
observer 
1
O is sitting at the centre of the circle 
and another observer 
2
O is sitting on the body. 
The centrifugal force is experienced by the 
observer 
(a) 
1
O only  (b) 
2
O only  
(c)  Both by 
1
O and 
2
O (d) None of these 
12. Find the maximum velocity for overturn for a car 
moved on a circular track of radius m 100 . The 
coefficient of friction between the road and tyre 
is 2 . 0    
(a) s m / 14 . 0  (b) s m / 140  
(c) s km / 4 . 1  (d) s m / 14 
13. When the road is dry and the coefficient of 
friction is ? , the maximum speed of a car in a 
circular path is s m / 10 . If the road becomes wet 
and 
2
?
? ? ? , what is the maximum speed 
permitted 
(a) s m / 5   (b) s m / 10  
(c) s m / 2 10  (d) s m / 2 5 
14. The coefficient of friction between the tyres and 
the road is 0.25. The maximum speed with which 
a car can be driven round a curve of radius 40 m 
with skidding is (assume g = 10 ms
–2
)    
(a) 
1
40
?
ms  (b) 
1
20
?
ms  
(c) 
1
15
?
ms  (d) 
1
10
?
ms 
15. A boy on a cycle pedals around a circle of 20 
metres radius at a speed of 20 metres/sec. The 
combined mass of the boy and the cycle is kg 90 . 
The angle that the cycle makes with the vertical 
so that it may not fall is       
(a) tan
-1
 (3)  (b) tan
-1
 (2)  
(c) tan
-1
 ( ?3)  (d) tan
-1
 ( ?2) 
 
M 
m 
 
O 
 
 
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