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 CHD:- SCO- 55-56 Second Floor, Sec- 20-C, Chandigarh. Phone:- 0172-5075556, 93161-33168 PKL: SCO-136, Sector-14, Behind Petrol Pump, Panchkula. Phone:- 9888894346, 93161-33168, 9915723880 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 lRead More

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