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 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 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 ?Read More

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