LAWS OF MOTION LAWS OF MOTION OBJECTIVE TYPE
LAWS OF MOTION
LAWS OF MOTION OBJECTIVE TYPE QUESTIONS CLASSWORK L-1
LAWS OF MOTION 1. A force of 12 N gives an object an acceleration of 4 ms– 2. The force required to give it an acceleration of 10 ms– 2 is 1) 15 N Solution: 2) 20 N 3) 25 N 4) 30 N
LAWS OF MOTION 1) 0. 01349 m/s 2 Solution: 2) 0. 1349 m/s 2 3) 1. 349 m/s 2 4) 13. 49 m/s 2
LAWS OF MOTION 3. A stream of water flowing horizontally with a speed of 15 ms– 1 rushes out of a tube of cross - sectional area 10– 2 m 2 and hits a vertical wall near by. What is the force exerted on the wall by the impact of water, assuming that it does not rebound ? (Density of water =1000 kg m– 3) 1) 2500 N 2) 2250 N 3) 2000 N 4) 1500 N Solution:
LAWS OF MOTION Solution: If the forces are acting simultaneously If these force keep the body in equilibrium
LAWS OF MOTION KEY: 4
LAWS OF MOTION 5. 'P' and 'Q' horizontally push in the same direction a 1200 kg crate. 'P' pushes with a force of 500 newton and 'Q' pushes with a force of 300 newton. If a frictional force provides 200 newton of resistance, what is the acceleration of the crate? Solution:
LAWS OF MOTION 6. A balloon has 8 gram of air. A small hole is pierced into it. The air escapes at a uniform rate of 7 cm/s. If the balloon shrinks in 5. 6 sec, then the average force acting on the balloon is 3) 56 dyne Solution:
LAWS OF MOTION 7. A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 ms– 1, comes to rest after 2 second. If one wants to keep this body moving on the same surface with a velocity of 4 ms– 1, the force required is 1) zero 2) 2 N 3) 4 N 4) 8 N Solution: V=u+at⇒ 0=4+a(2) F = ma = -2× 2=4 N
LAWS OF MOTION 8. A ship of mass 3000 kg initially at rest is pulled by a force of 1. 8 x 104 N through a distance of 3 m. Assuming that the resistance due to water is negligible the speed of the ship is 1) 1 ms– 1 Solution: 2) 5 ms– 1 3) 1. 5 ms– 1 u=0 4) 6 ms– 1
LAWS OF MOTION 9. A gun can exert an average force of 180 N, against the bullet and the gun fires 50 g bullets at a speed of 1 km/s. The bullet releasing capacity of the gun per minute is 1) 216 Solution: 2) 116 3) 416 4) 126
LAWS OF MOTION 10. A body of 2 kg has an initial speed 5 ms– 1. A force acts on it for 4 seconds in the direction of motion. The force time graph is shown in figure. The final speed of the body is F(N) 4 3 2 2 4 4. 5 6. 5 1) 9. 25 ms– 1 3) 12. 125 ms– 1 t(s) 2) 9. 125 ms– 1 4) 4. 25 ms– 1
LAWS OF MOTION Solution: Area under force –time graph V=12. 125 m/s KEY: 3
LAWS OF MOTION 11. Two blocks of masses 3 kg and 1 kg are kept in contact with each other on a frictionless horizontal surface. If a force of 10 N is applied on the larger block. What is the contact force between the two blocks? 4) 1 N 3) 3. 5 N 1) 2. 5 N 2) 3 N Solution: 10 N 3 Kg 1 Kg
LAWS OF MOTION Solution:
LAWS OF MOTION 1) 120 N Solution: 2) 240 N 3) 480 N 4) 720 N
LAWS OF MOTION 14. If m 1 = 10 kg; m 2 = 4 kg ; m 3 = 2 kg, the acceleration of system is Solution:
LAWS OF MOTION (1) + (2) (3) + (4) KEY: 3
LAWS OF MOTION 15. The acceleration of m 1 and m 2 are a 1 and a 2 then
LAWS OF MOTION Solution: KEY: 2
LAWS OF MOTION 16. Two objects of masses 2 kg and 3 kg are connected by a light string going over a light smooth pulley clamped at the top of a smooth inclined plane of inclination 30°. The object of mass 2 kg is hanging vertically and the other object is on the inclined plane. The acceleration of the system of two masses is 1) g/5 downwards 2) g/10 downwards 4) g/5 upwards 3) g/10 upwards Solution:
LAWS OF MOTION 17. In the above problem the tension in the string is 1) g N Solution: 2) 2 g N 3) 1. 8 g N 4) 0. 5 g N
LAWS OF MOTION 18. How can you lower a 100 kg body from the roof of a house using a cord with a breaking strength of 80 kg weight without breaking the rope ? (1 kg weight = g N) 1) 0. 98 m/s 2 Solution: 2) 1. 96 m/s 2 3) 2. 94 m/s 2 4) 4. 4 m/s 2
LAWS OF MOTION 19. A straight rope of length 'L' is kept on a frictionless horizontal surface and a force 'F' is applied to one end of the rope in the direction of its length and away from that end. The tension in the rope at a distance 'l' from that end is Solution:
LAWS OF MOTION 20. The average force necessary to stop a hammer with 25 N-S momentum in 0. 05 second expressed in newton is 1) 500 Solution: 2) 125 3) 50 4) 25
LAWS OF MOTION Solution:
LAWS OF MOTION 22. A man and a cart move towards each other. The man weighs 64 kg and the cart 32 kg. The velocity of the man is 5. 4 km/hr and that of the cart is 1. 8 km/hr. When the man approaches the cart, he jumps on to it. The velocity of the cart carrying the man will be 1) 3 km/hr Solution: 2) 30 km/hr 3) 1. 8 km/ hr 4) zero
LAWS OF MOTION 23. A 6000 kg rocket is set for vertical firing. if the exhaust speed of the rocket is 1000 ms– 1, then the gas eject per second to supply thrust needed to over come the weight of the rocket is 1) 68. 8 Kg/s Solution: 2) 48. 8 Kg/s 3) 58. 8 Kg/s 4) 18. 8 Kg/s
LAWS OF MOTION Solution:
LAWS OF MOTION 25. When a horizontal force of 10 N is applied on a body, it just begins to slide on a rough horizontal surface. If a horizontal force of 5 N is applied on it, then the frictional force acting on it is 4) 1 N 2) 5 N 1) 3 N 3) 2 N Solution: Frictional force = self adjusting as 5 N
LAWS OF MOTION 26. The horizontal force required to drag a wooden cube of a side ‘a’ on a rough horizontal surface is F. Another cube of the same wood but of side ‘ 2 a’ is dragged on the same surface. Then the force required if the cube is dragged with constant speed in both the cases is 1) 2 F Solution: m=d×V 2) 4 F 3) 6 F 4) 8 F
LAWS OF MOTION 27. A number of blocks each of mass 0. 4 Kg are placed one over the other. The minimum horizontal force required to pull the eigth block from the top without disturbing the remaining is 10 N. If g =10 ms– 2, the coefficient of static friction between any two blocks is. 1) 1/6 2) 1/3 Solution: F=(2 N-1)�� mg 10=(2× 8 -1)�� × 0. 4 × 10 3) 1/2 4) 1/4
LAWS OF MOTION 28. A block weighing 10 N rests on a horizontal surface. The coefficient of static friction between the block and the surface is 0. 4 and the coefficient of sliding friction is 0. 2. If a horizontal force of 2. 5 N is exerted on the block, the magnitude of the frictional force acting on the block is. 1) 2. 5 N 2) 1. 5 N Solution: 3) 6. 5 N 4) 4 N
LAWS OF MOTION 29. A book sits on horizontal top of a car as the car accelerates horizontally from rest. If the static coefficient of friction between car top and the book is 0. 45, the minimum acceleration of the car can have for the book not to slip is 1) 3. 92 ms– 2 2) 4. 41 ms– 2 3) 4. 9 ms– 2 4) 9. 8 ms– 2 Solution:
LAWS OF MOTION 30. A body of mass 2 kg is placed on a horizontal surface having coefficient of kinetic friction 0. 4 and coefficient of static friction 0. 5. If a horizontal force of 2. 5 N is applied on the body, the frictional force acting on the body will be (g=10 ms– 2) 1) 8 N Solution: 2) 10 N 3) 20 N 4) 2. 5 N
LAWS OF MOTION 31. In the above problem, the minimum force required to slide the body is 1) 8 N Solution: 2) 10 N 3) 20 N 4) 2. 5 N
LAWS OF MOTION 32. In the above problem, during the sliding motion of the body the frictional force is 3) 3. 20 N 1) 8 N 2) 10 N 4) 2. 5 N Solution:
LAWS OF MOTION 33. In the above problem the position of the body is 1) rest 3) acclerated motion Solution: 2) moving with uniform velocity 4) we cannot say
LAWS OF MOTION 34. In the above problem, if force applied on the body is 12 N, then its acceleration is 1) 5 ms– 2 Solution: 2) 4 ms– 2 3) 2 ms– 2 4) 0. 5 ms– 2
LAWS OF MOTION 35. In the above problem if force applied is 9 N its acceleration in ms– 2 is 1) 4. 5 2) 0. 4 Solution: ⇒Body remains at rest ⇒ a=0 3) 0. 25 4) Zero
LAWS OF MOTION 1) 2/3 g Solution: 2) 3/2 g 3) 3/g 4) 1/g
LAWS OF MOTION 37. The coefficient of friction is 0. 75. If sin 37° = 0. 6. The angle of friction is. Solution: �� =tan�� 5 3 4
LAWS OF MOTION 3) 1/2 Solution:
LAWS OF MOTION 39. A chain is kept on a table such that 1/3 of the length of the chain is hanging down. Then the coefficient of static friction between the chain and the table is. 4) 1/6 3) 1/4 2) 1/3 1) 1/2 Solution:
LAWS OF MOTION 40. A car running with a velocity 72 kmph on a level road, is stopped after travelling a distance of 30 m after disengiging its engine (g = 10 ms– 2). The coefficient friction between the road and the tyres is 2) 4. 5 3) 0. 67 1) 0. 33 4) 0. 8 Solution:
LAWS OF MOTION 1) 0. 2 Solution: 2) 0. 25 3) 0. 3 4) 0. 35
LAWS OF MOTION 42. A wooden block is placed on an inclined plane. The block just to slide when the angle of inclination is increased to 35°. Then the coefficient of friction would be 1) sin 35° Solution: 2) tan 53° 3) cot 55° 4) cot 35°
LAWS OF MOTION Solution:
LAWS OF MOTION N cosθ Solution: Ncos�� =mg N θ ) F N sinθ mg θ
LAWS OF MOTION 1) 5. 667 Solution: 2) 6. 66 3) 7. 66 4) Zero
LAWS OF MOTION 46. In the above problem the resultant force on the body is 1) 56. 6 N 2) 66. 6 N Solution: F=ma=10× 7. 67=76. 7 N 3) 76. 7 N 4) 86. 6 N
LAWS OF MOTION 47. In the above problem, the frictional force on the body is 1) Zero Solution: ⇒f=10 N 2) 5 N 3) 7. 5 N 4) 10 N
LAWS OF MOTION 48. In the above problem, the minimum force required to pull the body up the inclined plane 1) 66. 6 N Solution: 2) 86. 6 N 3) 96. 6 N 4) 76. 6 N
LAWS OF MOTION 49. In the above problem, if the length of the inclined plane 10 m then the work done to pull it to the top is 4) 966 J 2) 766 J 1) 666 J 3) 866 J Solution: W=F. S=96. 6× 10=966 J
LAWS OF MOTION 50. A body slides down a rough inclined plane of angle of inclination 30º and takes time twice as great as the time taken in slipping down a similar frictionless plane. The coefficient of friction between the body and the plane is 3) 4/3 Solution: 4) 3/4
LAWS OF MOTION 51. A block of ice at 00 C whose mass is 20 kg is dragged on the ground through a distance of 42 m. If the coefficient of friction between ice block and ground is 0. 2. The mass of the melted ice is(g = 10 ms– 2 and latent heat of fusion of ice = 80 × 4200 J/Kg). 1) 10 gm 2) 5 gm 3) 0. 5 gm Solution: W=Q �� Mgs=m. L ⇒ 0. 2× 20 × 10 × 42=m × 80 × 4200 4) 50 gm
LAWS OF MOTION Solution: mgsin�� =1× 9. 8 ×sin 30=4. 9 N
LAWS OF MOTION Solution:
LAWS OF MOTION m M Solution: a
LAWS OF MOTION 55. Two blocks A and B of masses 6 kg and 3 kg rest on a smooth horizontal surface as shown in the Fig. If coefficient of friction between A and B is 0. 4, the maximum horizontal force which can make them without separation is B F A 1) 72 N 2) 40 N Solution: 3) 36 N 4) 20 N
LAWS OF MOTION KEY: 3
LAWS OF MOTION Thank you…
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