Tiêu đề 05. NEWTONS LAWS OF MOTION med.pdf ✅

1. Inertia is that property of a body by virtue of which the body is (a) Unable to change by itself the state of rest (b) Unable to change by itself the state of uniform motion (c) Unable to change by itself the direction of motion (d) Unable to change by itself the state of rest or of uniform motion 2. A ball is travelling with uniform translator motion. This means that (a) It is at rest (b) The path can be a straight line or circular and the ball travels with uniform speed (c) All parts of the ball have the same velocity (magnitude and direction) and the velocity is constant (d) The centre of the ball moves with constant velocity and the ball spins about its centre uniformly 3. Which of the following cases the net force acting on the body is not zero? (a) A drop of rain falling down with a constant speed (b) A cork of mass 10 g floating on the surface of water (c) A car moving with a constant speed of 1 20 km h − on a Rough road: (d) A pebble of mass 0.05 kg is thrown vertically upwards 4. Which one of the following statements is not true about Newton’s second law of motion F ma   = ? (a) The second law of motion is consistent with the first law (b) The second law of motion is a vector law (c) The second law of motion is applicable to a single point particle (d) The second law of motion is not a local law 5. A bullet of mass 40 g moving with a speed of 1 90 m s − enters a heavy wooden block and is stopped after a distance of 60 cm. The average resistive force exerted by the block on the bullet is : (a) 180 N (b) 220 N (c) 270 N (d) 320 N 6. A ball of mass m strikes a rigid wall with speed u and rebounds with the same speed. The impulse imparted to the ball by the wall is (a) 2mu (b) Mu (c) Zero (d) -2mu 7. A body under the action of a force F = 6 ˆ i −8 ˆ j N  acquires an acceleration of 2 5 m s − . The mass of the body is (a) 2 kg (b) 5 kg (c) 4 kg (d) 6 kg 8. A large force is acting on a body for a short time. The impulse imparted is equal to the change in (a) Acceleration (b) Momentum (c) Energy (d) Velocity 9. The motion of particle of mass m is given by 2 gt 2 1 y = ut + . The force acting on the particle is (a) mg (b) t mu (c) 2mg (d) t 2mu 10. Which one of the following is not force? (a) Impulse (b) Tension (c) Thrust (d) Weight 11. A constant retarding force of 50 N is applied to a body of mass 10 kg moving initially with a speed of 1 10 m s − . The body comes to rest after (a) 2 s (b) 4 s (c) 6 s (d) 8 s 12. A constant force acting on a body of mass of 5 kg change its speed from 1 5 m s − to 1 10 m s − in 10 s without changing the direction of motion. The force acting on the body is : (a) 1.5 N (b) 2 N (c) 2.5 N (d) 5 N 13. The relation F ma,   = cannot be deduced from Newton’s second law, if : (a) Force depends on time (b) Momentum depends on time (c) Acceleration depends on time (d) Mass depends on time 14. The dimensions of reaction are : (a)   2 3 M LT− (b)   1 MLT− (c)   2 MLT− (d)   2 1 ML T − 15. A cork of mass 10 g is floating on water. The net force acting on the cork is : (a) 10 N (b) 10 N −3 (c) 10 N −2 (d) Zero 16. A stone of mass 1 kg is lying on the floor of a train which is accelerating with 2 1 m s − . The net force acting on the stone is : (a) Zero (b) 1 N (c) 5 N (d) 10 N 17. Which of the following statements is incorrect? (a) A cricketer moves his hands backwards while holding a catch (b) A person falling from a certain height receives more injuries when he falls on a cemented floor than when he falls on a heap of sand (c) It is easier to push a lawn mower than to pull it (d) Mountain roads are generally made winding upwards rather than going straight up 18. Which one of the following statements is not true? (a) The same force for the same time causes the same change in momentum for different bodies (b)The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts (c) A greater opposing force is needed to stop a heavy body than a light body in the same time, if they are moving with the same speed (d) The greater the change in the momentum in a given time, the lesser is the force that needs to be applied 19. A body subjected to three concurrent forces is found to be in equilibrium. The resultant of any two forces : (a) Is equal to third force (b) Is opposite to third force (c) Is collinear with the third force
(d) All of these 20. A body is moving under the action of two forces j ˆ i 4 ˆ j; F 3 ˆ i 5 ˆ F1 = 2 − 2 = −   . Its velocity will become uniform under a third force F3  given by : (a) j ˆ i ˆ 5 − (b) j ˆ i ˆ − 5 − (c) j ˆ i ˆ 5 + (d) j ˆ i ˆ − 5 + 21. Three concurrent co-planar forces 1 N, 2 N and 3 N acting along different directions on a body : (a) Can keep the body in equilibrium if 2 N and 3 N act at right angle (b) Can keep the body in equilibrium if 1 N and 2 N act at right angle (c) Cannot keep the body in equilibrium (d) Can keep the body in equilibrium if 1 N and 3 N act at an acute angle 22. Which of the following statements is correct about friction? (a) The coefficient of friction between a given pair of substances is largely independent of the area of contact between them (b) The frictional force can never exceed the reaction force on the body from the support surface (c) Rolling friction is only slightly smaller than sliding friction (d) The main source of friction is the irregularity of the surfaces in contact 23. A girl presses her physics text book against a rough vertical wall with her hand. The direction of the frictional force on the book exerted by the wall is : (a) Downwards (b) Upwards (c) Out from the wall (d) Into the wall 24. A car accelerates on a horizontal road due to the force exerted by : (a) The engine of the car (b) The driver of the car (c) The car on earth (d) The road on the car 25. A block of mass 1 kg lies on a horizontal surface in a truck. The coefficient of static friction between the block and the surface is 0.6. If the acceleration of the truck is 2 5 m s − . The frictional force acting on the block is : (a) 10 N (b) 5 N (c) 2.5 N (d) 20 N 26. Which of the following is a self adjusting force? (a) Static friction (b) Rolling friction (c) Sliding friction (d) Dynamic friction 27. Which one of the following can also act as a lubricant in the machines? (a) Iron fillings (b) Polish on machines (c) Flow of water through the machine (d) Flow of compressed and purified air 28. A block of mass m rests on a rough inclined plane. The coefficient of friction between the surface and the block is  . At what angle of inclination  of the plane to the horizontal will the block just start to slide down the plane? (a)  =  −1 tan (b)  =  −1 cos (c)  =  −1 sin (d)  =  −1 sec 29. Identify the correct statement : (a) Static friction depends on the area of contact (b) Kinetic friction depends on the area of contact (c) Coefficient of static friction does not depend on the surfaces in contact (d) Coefficient of kinetic friction is less than the coefficient of static friction 30. One end of a string of length l is connected to a particle of mass m and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed v, the net force on the particle directed towards the centre is : (where T is the tension in the string) (a) T (b) l mv T 2 − (c) l mv T 2 + (d) 0 31. A cyclist bends while taking turn to : (a) Reduce friction (b) Generate required centripetal force (c) Reduce apparent weight (d) Reduce speed 32. A small object placed on a rotating horizontal turn table just slips when it is placed at a distance 4 cm from the axis of rotation. If the angular velocity of the turn-table is doubled, the object slips when its distance from the axis of rotation is : (a) 1 cm (b) 2 cm (c) 4 cm (d) 8 cm 33. A particle is moving on a circular path of 10 m radius. At any instant of time, its speed is 2 2 m s − . The magnitude of net acceleration at this instant is : (a) 2 5 m s − (b) 2 3.2 m s − (c) 2 2 m s − (d) 2 4.3 m s − 34. A motor cyclist rides around the well with a round vertical wall and does not fall down while riding because : (a) The force of gravity disappears (b) He loses weight some how (c) He is kept in this path due to the force exerted by surrounding air (d) The frictional force of the wall balances his weight 35. In the system shown in the figure, the acceleration of 1kg mass is : (a) downwards 4 g (b) downwards 2 g
(c) upwards 2 g (d) upwards 4 g 36. A ball is travelling with uniform translator motion. This means that (a) It is at rest (b) The path can be a straight line or circular and the ball travels with uniform speed. (c) All parts of the ball have the same velocity (magnitude and direction) and the velocity is constant. (d) The centre of the ball moves with constant velocity and the ball spins about its centre uniformly. 37. A metre scale is moving with uniform velocity. This implies. (a) The force action on the scale is zero. But a torque about the centre of mass can act on the scale. (b) The force acting on the scale is zero and the torque acting about centre of mass of the scale is also zero. (c)The total force acting on it need not zero but the torque on it is zero. (d) Neither the force nor the torque need to be zero. 38. Conservation of momentum in a collision between particles can be understood from (a) Conservation of energy. (b) Newton’s first law only. (c) Newton’s second law only. (d) Both Newton’s second and third law. 39. A hockey player is moving north ward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on the player is. (a) Frictional force along westward. (b) Muscle force along southward. (c) Frictional force along south west. (d) Muscle force along south – west. 40. An astronaut accidentally gets separated out of his small spaceship accelerating in interstellar space at a constant rate of 2 100 m s − . What is the acceleration of the astronaut the instant after he is outside the spaceship? (Assume that there are no nearby stars to exert gravitational force on him) (a) Zero (b) 2 10 m s − (c) 2 50 m s − (d) 2 100 m s − 41. A batman hits back a ball of mass 0.15 kg straight in the direction of the bowler without changing its initial speed of 1 12 m s − . If the ball moves linearly, then the impulse imparted to the ball is (a) 1.8Ns (b) 2.8Ns (c) 3.6Ns (d) 4.2 Ns 42. Figure shows the position-time (x-t) graph of one dimensional motion of a body of mass 500 g. What is the time interval between two consecutive impulses received by the body? (a) 2 s (b) 4 s (c) 6 s (d) 8 s 43. A body of mass 5 kg starts from the origin with an initial velocity 1 j) m s ˆ i 40 ˆ u (30 − = +  . If constant force (−6 ˆ i − 5 ˆ j) N acts on the body, the time in which the y- component of the velocity becomes zero is : (a) 5 s (b) 20 s (c) 40 s (d) 80 s 44. A body of mass 0.4 kg starting at origin at t = 0 with a speed of 1 10 m s − in the positive x-axis direction is subjected to a constant F = 8 N towards negative x-axis. The position of the body after 25 s is : (a) -6000 m (b) -8000 m (c) +4000 m (d) +7000 m 45. The position-time graph of a body of mass 2 kg is as shown in figure. What is the impulse on the body at t 4 s? (a) kg m s 1 3 2 − (b) 1 kg m s 3 2 − − (c) 1 kg m s 2 3 − (d) 1 kg m s 2 3 − − 46. The figure shows (x, t), (y, t) diagram of a particle moving in 2-dimensions. If the particle has a mass of 500 g, the force acting on the particle is : (a) 1 N along y-axis (b) 1 N along x-axis (c) 0.5 N along x-axis (d) 0.5 N along y-axis 47. Figure shows the position-time graph of a particle of mass 4 kg. Let the force on the particle for 2 t  0, 0  t  4 s, t F 4 , be F1  s and F3 respectively. Then: (a) F1 = F2 = F3 = 0 (b) F1  F2 = F3 (c) F1  F2  F3 (d) F1  F2  F3
48. A rocket is going upwards with accelerated motion. A man sitting in it feels his weight increased 5 times his own weight. It the mass of the rocket including that of the the man is 1.0 10 kg 4  , how much force is being applied by rocket engine? (Take g = 2 10 m s − ) (a) 5 10 N 4  (b) 5 10 N 5  (c) 5 10 N 8  (d) 2 10 N 4  49. When a speeding bus stops suddenly, passengers are thrown forward from their seats because : (a) The back of seat suddenly pushes the passengers forward (b) Inertia of rest stops the bus and takes the body forward (c) Upper part of the body continues to be in the state of motion whereas the lower part of the body in contact with seat remains at rest (d) Upper part of the body come to rest whereas the lower part of the body in contact with seat begins to move 50. Ten one-rupee coins are put on top of each other on a table. Each coin has a mass m. The reaction of the 6th coin (counted from the bottom) on the 7th coin is : (a) 4mg (b) 6mg (c) 7mg (d) 3mg 51. A rocket of initial mass 6000 kg ejects gases at a constant rate of 1 16 kg s − with constant relative speed of 1 11 kg s − .What6 is the acceleration of the rocket one minute after the blast? (a) 2 25 m s − (b) 2 50 m s − (c) 2 10 m s − (d) 2 35 m s − 52. A stream of water flowing horizontally with a speed of 1 15 m s − gushes out of a tube of cross-sectional area 2 2 10 m − , and hits a vertical wall normally. Assuming that it does not rebound from the wall, the force exerted on the wall by the impact of water is : (a) N 3 1.25 10−  (b) 2.25 10 N −3  (c) 3.25 10 N −3  (d) 4.25 10 N −3  53. If the force on a rocket, moving with a velocity of 1 300 m s − is 210, then the rate of combustion of the fuel is : (a) 1 0.07 kg s − (b) 1 1.4 kg s − (c) 1 0.7 kg s − (d) 1 10.7 kg s − 54. Two billiard balls A and B, each of mass 50 g and moving in opposite directions with speed of 1 5 m s − each, collide and rebound with the same speed. The impulse imparted to each ball is : (a) 1 0.25 kg m s − (b) 1 0.5 kg m s − (c) 1 0.1 kg m s − (d) 1 0.125 kg m s − 55. A rocket with a lift-off mass 2 10 N 5  kg is blasted upwards with an initial acceleration of 2 5 m s − . The initial thrust of the blast is (Take 2 g 10 m s − = ) : (a) 2 10 N 5  (b) 3 10 N 5  (c) 4 10 N 5  (d) 5 10 N 5  56. Match Column I with Column II : Column I Column II (A) Definition of force (p) Newton’s third law (B) Measure of force (q) Impulse (C) Effect of force (r) Newton’s second Law (D) Recoiling of gun (s) Newton’s first law (a) A − q,B− p,C− r,D − s (b) A − p,B− q,C− r,D − s (c) A − s,B− r,C− q,D − p (d) A − s,B− q,C− r,D − p 57. A ball of mass m strikes a rigid wall with speed u at an angle of o 30 and get reflected with the same speed and at the same angle as shown in the figure. If the ball is in contact with the wall for time t, then the force acting on the wall is : (a) t mu sin 30o (b) t 2mu sin 30o (c) t mu cos30o (d) t 2mu cos30o 58. A steam of water flowing horizontally with a speed of 1 20 m s − gushes out of a tube of cross-sectional area 3 2 10 m − , and hits at a vertical wall nearby. What is the force exerted on the wall by the impact of water? (a) 125 N (b) 625 N (c) -650 N (d) -1125 N 59. A 100 kg gun fires a ball of 1 kg horizontally from a cliff of height 500 m. It falls on the ground at a distance of 400 m from the bottom of the cliff. The recoil velocity of the gun is : (Take 2 g 10 m s − = ) (a) 1 0.2 m s − (b) 1 0.4 m s − (c) 1 0.6 m s − (d) 1 0.8 m s − 60. A shell of mass 200 g is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 1 80 m s − , then the recoil speed of the gun is : (a) 1 16 cm s − (b) 1 8 cm s −