Physics-MC 2006-7 Page 1 of 29 Inertia, Force and Motion 1. 3. 2. Three blocks of equal mass are placed on a smooth horizontal surface as shown in the figure above. A constant force F is applied to block A so that the three blocks move towards the right with the same acceleration. The net force acting on the block B is A. 0 F B. 1 3 F C. 1 2 F D. 2 3 F E. 1 F 4. Two blocks of equal mass are placed on a smooth horizontal surface as shown above. A constant force of 12 N is applied to block A so that the two blocks move towards the right together. The force acting on A by B A. zero. B. 6 N to the left. C. 6 N to the right. D. 12 N to the left. E. 12 N to the right. Y has a linear relationship with time as shown. Y may represent (1) the speed of a body starting from rest under a constant force. (2) the distance travelled by a body at constant speed. (3) the acceleration of a body falling from rest. The diagram above shows the variation of the net force acting on an object which is initially at rest. Which of the following velocity-time graphs correctly describes the motion of the object?
Physics-MC 2006-7 Page 2 of 29 5. A force F is applied to a block of mass 1 kg as shown above. The GREATEST value of F for the block to remain at rest is 11 N. What would be the motion of the block if F is not applied? A. remaining at rest B. sliding down with constant velocity C. sliding down with an acceleration of 1 m s 2. D. sliding down with an acceleration of 5 m s 2. E. sliding down with an acceleration of 6 m s 2. 6. A man of weight W stands inside a lift which is moving upwards with a constant speed. If the force exerted by the floor on the man is R, which of the following statements is/are correct? (1) R is greater than W in magnitude. (2) R and W are in opposite directions. (3) R and W form an action and reaction pair according to Newton s third law. B. (2) only C. (1) and (3) only
Physics-MC 2006-7 Page 3 of 29 7. Two identical blocks X and Y are connected by a light string passing over a smooth pulley as shown above. The two blocks are released from rest. After a while, the string breaks. Which of the following correctly describes the motion of the blocks immediately after the string breaks? X stops moving moves with constant velocity accelerates at 5 ms 2 moves with constant velocity decelerates at 5 ms 1 Y accelerates at 5 ms 2 accelerates at 5 ms 2 moves with constant velocity accelerates at 10 ms 2 accelerates at 10 ms 2 8. In the above diagram, blocks A and B are connected by a light inextensible string and rest on a smooth horizontal table. The masses of A and B are 2 kg and 3 kg respectively. Block A is pulled by a force of 2 N. Find the tension in the string S. A. 0.4 N B. 0.8 N C. 1.0 N D. 1.2 N E. 2.0 N
Physics-MC 2006-7 Page 4 of 29 9. Which of the following pairs of forces F 1 and F 2 is/are action and reaction pair(s) according to Newton s third law of motion? A. (2) only D. (1) and (3) only
Physics-MC 2006-7 Page 5 of 29 10. 12. A trolley is given a push and runs down a friction-compensated runway. The motion of the trolley is recorded on the paper tape as shown above. Which of the following changes can enable the trolley to produce a paper tape as shown below? (1) Giving the trolley a harder initial push (2) Increasing the angle of inclination of the runway (3) Increasing the frequency of the ticket-tape timer 11. A man of mass 50 kg is standing in a lift. If the lift is falling freely, which of the following statements is/are true? (1) The weight of the man is 0 N. (2) The force acting on the floor of the lift by the man is 500 N. (3) The force acting on the man by the floor of the lift is 0 N. Two blocks X and Y of weights 2 N and 8 N respectively are suspended by two light strings as shown above. A downward force of 4 N is applied to X. Find the tensions T 1 and T 2 in the two strings. T 1 T 2 A. 2 N 8 N B. 4 N 10 N C. 4 N 14 N D. 6 N 12 N E. 6 N 14 N 13. Which of the following statements about mass and weight is incorrect? A. Mass is measured in kilograms and weight in newtons. B. Mass is a scalar while weight is a vector. C. Mass is a measure of the inertia of an object and weight is a measure of the gravitational pull on it. D. The weight of an object at a particular place is proportional to its mass. E. Both the mass and weight of an object vary slightly at different places on the earth.
Physics-MC 2006-7 Page 6 of 29 14. 16. smooth horizontal surface In the above diagram, the two blocks are connected by a light string S. They move with uniform acceleration of 2 m s 2 under the action of a constant force F. What will the accelerations of the blocks become if S suddenly breaks? 2 kg block 4 kg block A. 6 m s 2 0 m s 2 B. 6 m s 2 2 m s 2 C. 2 m s 2 0 m s 2 D. 2 m s 2 2 m s 2 E. 0 m s 2 3 m s 2 15. Which of the following statements concerning the motion of an object is/are correct? (1) A constant unbalanced force is needed to keep an object moving with uniform velocity. (2) An increasing unbalanced force is needed to keep an object moving with uniform acceleration. (3) An object may remain at rest if there is no unbalanced force acting on it. A. (2) only D. (1) and (3) only The above diagram shows a block resting on the ground. Let W be the weight of the block, F be the gravitational force acting on the earth by the block, and R be the force acting on the block by the ground. Which of the following pairs of forces is/are action and reaction pair(s) according to Newton s third law of motion? (1) R and W (2) W and F (3) F and R B. (2) only C. (3) only D. (1) and (2) only E. (2) and (3) only
Physics-MC 2006-7 Page 7 of 29 17. 19. A coin and a feather are released from rest in vacuum as shown above. Which of the following is/are correct deductions from this experiment? (1) The masses of the coin and the feather are identical in vacuum. (2) The coin and the feather fall with the same acceleration in vacuum. (3) The forces acting on the coin and the feather in vacuum are identical. B. (2) only C. (1) and (3) only 18. A girl in a lift uses a spring balance to measure the weight of an object. The reading of the spring balance is 10 N when the lift is at rest. When the lift is moving, the reading of the spring balance becomes 8 N. Which of the following describes the motion of the lift? A. moving upwards with a uniform velocity B. moving downwards with a uniform velocity C. moving upwards with an acceleration D. moving downwards with an acceleration E. moving downwards with a deceleration The above diagram shows a man lifting a ball vertically upwards with uniform acceleration. Let F 1 be the force acting on the ball by the man, F 2 be the force acting on the man by the ball, F 3 be the gravitational force acting on the ball. Which of the following correctly describes the relation between the magnitudes of the forces? A. F 1 = F 2 > F 3 B. F 1 = F 3 > F 2 C. F 1 > F 2 = F 3 D. F 1 > F 2 > F 3 E. F 1 > (F 2 + F 3 ) 20. Which of the following phenomena can be explained by Newton s first law of motion? (1) A passenger in a car tends to move forward when the car suddenly stops. (2) A coin and a feather fall with the same acceleration in a vacuum. (3) A gun recoils when it fires a bullet. B. (2) only C. (1) and (3) only
Physics-MC 2006-7 Page 8 of 29 21. Which of the following pairs of forces is/are action and reaction pair(s) according to Newton s third law of motion? (1) The weight of a man standing on a chair. (2) The gravitational force acting on the earth by the moon. (3) The force exerted by a swimmer on the water to push the water backward. B. (2) only C. (1) and (3) only and and and The force acting on the man by the chair. The gravitational force acting on the moon by the earth. The force exerted by the water to push the swimmer forward. 22. A broken-down car of mass 1000 kg is pulled by a tow-truck and moves at a constant velocity 8 m s 1 along a horizontal road. It is known that the frictional force acting on the car is 500 N. Find the tension in the cable connecting the truck and the car. A. 0 N B. 500 N C. 8 000 N D. 8 500 N E. 10 500 N
Physics-MC 2006-7 Page 9 of 29 More About Forces 1. A solid cube exerts a pressure P on the table. What is the pressure exerted by another cube of the same material but with all the dimensions doubled? 2. A. P 4 B. P 2 C. P D. 2P E. 4P 4. A block remains at rest on an inclined plane as shown above. Which of the following statements is/are true? (1) The frictional force acting by the plane on the block is zero. (2) The normal reaction acting by the plane on the block is zero. (3) The resultant force acting on the block is zero. A. (2) only D. (1) and (3) only 3. A trolley is placed on a horizontal ground. A force F inclined at an angle θ to the horizontal acts on the trolley. What is the horizontal component of F that pulls the trolley towards the right? A. Fθ B. Fsinθ C. Fcosθ F D. sinθ F E. cosθ A block is placed on a smooth inclined plane. A force P parallel to the inclined plane is applied to the block so that the block moves up the plane. Which of the following diagrams correctly shows all the forces acting on the block?
Physics-MC 2006-7 Page 10 of 29 5. Scale : 1 cm represents 1 N Two forces F 1 and F 2 act on a particle P as shown above. If a third force F 3 acts on P to keep it in equilibrium, find the magnitude of F 3. A. 1.4 N B. 4.0 N C. 4.2 N D. 4.5 N E. 5.8 N
Physics-MC 2006-7 Page 11 of 29 Speed, Velocity and Acceleration 1. 3. A coin and a feather are allowed to fall in a long vertical glass tube from which the air has been evacuated. Which one of the following combinations best describes the motion of the coin and the feather? Coin Feather The figure above shows the stroboscopic photograph of a ball rolling down a slope. If the stroboscope makes 2 flashes per second, in which region does the ball have an average speed of 40 cm s 1? A. KL B. LM C. MN D. NO E. OP 2. An object is falling from rest with an acceleration of 10 m s 2. Which of the following statements is/are correct? (1) It falls with a constant speed of 10 m s 1. (2) It falls 10 m every second. (3) It has a speed of 20 m s 1 after 2 s. 4. A. uniform speed same uniform speed B. uniform speed greater uniform speed C. uniform acceleration same uniform acceleration D. uniform acceleration smaller uniform acceleration E. uniform acceleration greater uniform acceleration The above graph shows how the square of velocity of an object undergoing uniform acceleration varies with displacement. The object is initially at rest and travels along a straight line. The acceleration of the object is A. 0.5 m s 2 B. 1.0 m s 2 C. 2.0 m s 2 D. 4.0 m s 2 E. 8.0 m s 2
Physics-MC 2006-7 Page 12 of 29 5. 6. The figure above shows the strobe photograph of a ball rolling down a slope. The stroboscope is flashing at a frequency of 5 Hz. Find the acceleration of the ball. A. 0.20 m s 2 B. 0.50 m s 2 C. 0.67 m s 2 D. 1.00 m s 2 E. 1.33 m s 2 A man takes 2 seconds to walk from point A to point B, and then takes 3 seconds to walk from point B to point C, where ABC is an equilateral triangle of side 3 m. Find the magnitude of his average VELOCITY from A to C. A. 0.60 ms 1 B. 1.00 ms 1 C. 1.20 ms 1 D. 1.25 ms 1 E. 1.50 ms 1
Physics-MC 2006-7 Page 13 of 29 7. The above figure shows the velocity-time graph of an object. Which of the following statements about the object is/are true? (1) Its acceleration in the first 10 seconds is 2 m s 2. (2) The total distance travelled is 250 m. (3) It returns to its starting point after 25 seconds. B. (2) only C. (1) and (3) only 8. A particle is thrown vertically upwards. When the particle is at the maximum height, its acceleration is A. zero. B. changing from upwards to downwards. C. changing from downwards to upwards. D. pointing upwards. E. pointing downwards.
Physics-MC 2006-7 Page 14 of 29 9. Which of the following displacement-time graphs describes the motion of a particle moving in a straight line with uniform deceleration? 11. An object is thrown vertically upwards from a point A. It travels to the highest point B and then falls back to A. Neglecting air resistance, which of the following statements is/are true? (1) The total displacement of the object is zero. (2) The acceleration of the object is constant throughout the motion. (3) The time for the upward motion is longer than the time for the downward motion. 12. Ans.: C 10. A car moves with a speed 30 km h 1. The driver applies the brake and the car is stopped in a distance of 12 m. If the car is moving at 60 km h 1, what is the stopping distance? Assume that the same constant braking force is applied in both cases. A. 12 m B. 24 m C. 48 m D. 72 m E. 96 m Figure (a) shows a man near the edge of a cliff projecting a stone vertically upwards. The stone reaches the sea after 18 seconds. Figure (b) shows the velocity-time graph for the motion of the stone. Find the height of the cliff. A. 180 m B. 540 m C. 720 m D. 900 m E. 1620 m
Physics-MC 2006-7 Page 15 of 29 13. 14. A man takes 30 s to walk 80 m towards the east. He then takes 10 s to run 60 m towards the south. Which of the following statements is/are correct? (1) The magnitude of the resultant displacement of the man is 140 m. (2) The average speed of the man is 4.3 m s 1. (3) The magnitude of the average velocity of the man is 2.5 m s 1. The above diagram shows the variation of the acceleration of an object which is initially at rest. Which of the following velocity-time graphs correctly describes the motion of the object? 15. An object moves with uniform acceleration along a straight line. Which of the following graphs correctly describe(s) the motion of the object? B. (2) only C. (1) and (3) only
Physics-MC 2006-7 Page 16 of 29 16. An object starts from rest and moves with uniform acceleration along a straight line. Which of the following graphs concerning the motion of the object is/are correct? (s = displacement, v = velocity, t = time) 18. Two objects of different masses are released from rest at the same height. Assume air resistance is negligible. Which of the following statements is/are correct? (1) A greater gravitational force is acting on the object with greater mass. (2) They take the same time to reach the ground. (3) They have equal velocities when they reach the ground. B. (2) only C. (1) and (3) only 19. 17. A man walks 40 m towards the west. He then walks 40 m towards the south and lastly walks 70 m towards the east. Find the magnitude of the resultant displacement of the man. A. 30 m B. 40 m C. 50 m D. 70 m E. 150 m A student walks along a curve ABC, which is made up of two semi-circular parts AB and BC of radius 3 m and 4 m respectively. He takes 2 s to walk from A to B and 5 s to walk from B to C. Find the magnitude of the average velocity of the student from A to C. A. 1.0 m s 1 B. 2.0 m s 1 C. 2.3 m s 1 D. 3.1 m s 1 E. 3.6 m s 1
Physics-MC 2006-7 Page 17 of 29 20. 22. The velocity-time graph of a car travelling along a straight horizontal road is shown above. Which of the following graphs shows the variation of the acceleration a of the car with time t? The above diagram shows the variation of the velocity of an object with time. What is the distance travelled by the object in the first 3 seconds? A. 5 m B. 15 m C. 25 m D. 30 m E. 45 m 21. A particle is released from rest and falls vertically under gravity. If the distance travelled by the particle in the 1st second is x and that travelled in the 2nd second is y, find the ratio x : y. A. 1 : 1 B. 1 : 2 C. 1 : 3 D. 1 : 4 E. 1 : 5
Physics-MC 2006-7 Page 18 of 29 23. A car undergoes uniform deceleration along a straight road. Its velocity decreases from 30 m s 1 to 20 m s 1 after travelling a distance of 100 m. How much further will the car travel before it comes to a rest? A. 50 m B. 80 m C. 180 m D. 200 m E. 300 m 24. At time t = 0, a table-tennis ball is released from a point above the ground and bounces several times on the ground. The above graph shows the variation of the velocity v of the ball with time t. (Note: Velocity pointing upwards is taken to be positive.) At which of the following points on the graph does the ball reach its maximum height above the ground after the first rebound? A. Point P B. Point Q C. Point R D. Point S E. Point T
Physics-MC 2006-7 Page 19 of 29 25. A small metal ball is released from a point above the floor and bounces several times. Which of the following graphs best represents the variation of the velocity of the ball with time?
Physics-MC 2006-7 Page 20 of 29 Work, Energy and Power 1. 2. The figure above shows an inclined plane with Y being midway between XZ. Two particle A and B of the same mass are released from rest at X and Y respectively. Which of the following statements about A and B is/are true? (1) The time required for A to reach Z is double that for B to reach Z. (2) The potential energy for A at Z is double that for B at Z. (3) The kinetic energy for A at Z is double that for B at Z. The above diagram shows two trolleys moving towards each other along a smooth runway. After collision, they stick together. What is the total loss in kinetic energy by the trolleys? A. 3 J B. 6 J C. 9 J D. 12 J E. 15 J
Physics-MC 2006-7 Page 21 of 29 3. 5. The figure above shows a mass m connected to another mass M by a string passing over a smooth pulley. The system is moving freely under gravity. Assuming that the table is smooth, which of the following statements is/are correct? (1) m and M move with the same acceleration in magnitude. (2) The loss in potential energy of m is equal to the gain in kinetic energy of M. (3) If the mass of M is doubled, its acceleration is halved. 4. Two metal spheres of unequal masses are released form rest at the same time from a height of 2 m above the ground. When they have fallen 1 m, (neglecting air resistance) they have the same A. speed. B. momentum. C. weight. D. kinetic energy. E. potential energy. The figure above shows a trolley of mass 1 kg being released from rest from point X of a rough slope. Its speed at Y is 3 m s 1. What is the loss in energy by the trolley when it is moving from X to Y? A. 1.0 J B. 4.5 J C. 5.5 J D. 9.0 J E. 10.0 J 6. Which of the following statements is/are correct when a collision between two particles is elastic? (1) None of the original kinetic energy is converted into other forms of energy. (2) The linear momentum of each particle is conserved. (3) The mechanical energy of each particle is conserved.
Physics-MC 2006-7 Page 22 of 29 7. An object slides down a smooth plane from rest as shown in the figure above. Which of the following graphs best shows the variation of kinetic energy with time?
Physics-MC 2006-7 Page 23 of 29 8. 10. Two objects P and Q of mass 0.1 kg and 0.5 kg respectively, are thrown vertically upwards with the same speed from the same level. Neglecting air resistance, Which of the following is true? Two equal masses A and B are connected by a light string passing over a smooth pulley as shown in the figure above. The inclined plane is smooth. Which of the following statements is/are correct? (1) The potential energy lost by A is equal to the potential energy gained by B. (2) The kinetic energy gained by A is equal to the kinetic energy gained by B. (3) The potential energy lost by A is equal to the sum of kinetic energies gained by A and B. 11. A. P will reach a point higher than that of Q. B. Q will take a shorter time to reach its highest point. C. Both will have the same potential energy at the highest point. D. Both will have the same kinetic energy on returning to the starting point. E. Both rise with the same deceleration. B. (2) only C. (3) only D. (1) and (2) only E. (2) and (3) only 9. A block of mass 5 kg is moving horizontally on a smooth surface in a straight line at 6 m s 1. In order to change its speed to 10 m s 1, the work done would need to be A. 40 J B. 90 J C. 160 J D. 400 J E. 550 J For a body falling freely under gravity, Y has a linear relationship with the displacement of the body as shown above. Y may represent A. the potential energy of the body. B. the kinetic energy of the body. C. the acceleration of the body. D. the velocity of the body. E. the speed of the body. 12. A block is pulled along a horizontal bench at a constant velocity of 10 m s 1 by a force of 5 N. What is the work done against friction in 4 seconds? A. 200 J B. 50 J C. 20 J D. 12.5 J E. 8 J
Physics-MC 2006-7 Page 24 of 29 13. Which of the following is/are vectors? 16. (1) momentum (2) kinetic energy (3) potential difference B. (2) only C. (1) and (3) only 14. A gas molecule collides with the wall of a container and bounces back with the same speed. Which of the following quantities of the molecule remain(s) unchanged before and after the collision? A trolley of mass 2 kg moves with a uniform speed of 4 ms 1 along a horizontal table. A lump of plasticine having the same mass as the trolley is dropped from a height slightly above the trolley and sticks to it. Find the total loss in kinetic energy. A. 0 J B. 4 J C. 8 J D. 12 J E. 16 J (1) kinetic energy (2) velocity (3) momentum 17. B. (2) only C. (1) and (3) only 15. Which of the following involve(s) an energy transfer of 100 J? (1) A mass of 10 kg is raised vertically by 10 m. (2) A mass of 2 kg gains a speed of 10 ms 1 from rest. (3) A 10 W heater is switched on for 10 seconds. A bell is released from rest from one end of a smooth curved rail as shown in the above diagram. Neglecting air resistance and friction, which of the following statements about the motion of the ball is/are correct? (1) The ball has maximum kinetic energy at point B. (2) The speed of the ball at point C is the same as that at point A. (3) The ball would not rise to a level higher than point D. B. (2) only C. (1) and (3) only
Physics-MC 2006-7 Page 25 of 29 18. 20. Which of the following pairs of physical quantities has/have the same unit? (1) Work and potential energy (2) Moment and momentum (3) Specific heat capacity and specific latent heat of fusion 19. The figure above shows the variation of the force acting on an object. What physical quantity does the area of the shaded portion represent? A. Velocity B. Acceleration C. Momentum D. Work E. Power A pendulum bob is released from rest from a point P 0.8 m above its lowest position Q, as shown in the above diagram. Neglecting air resistance, find the speed of the bob when it reaches Q. A. 2.8 m s 1 B. 4 m s 1 C. 8 m s 1 D. 16 m s 1 E. It cannot be determined since the mass of the bob is not given 21. A stone is thrown vertically upwards and it finally falls back to the starting point. Assume air resistance is negligible. Which of the following statements is/are true throughout the motion? (1) The acceleration of the stone is constant. (2) The total energy of the stone is conserved. (3) The momentum of the stone is conserved. 22. Which of the following expressions does not represent energy? A. Force displacement 1 B. mass (speed)2 2 C. (Current) 2 resistance D. Current potential difference time E. Mass specific latent heat of fusion
Physics-MC 2006-7 Page 26 of 29 23. A stone is projected vertically upwards. Neglecting air resistance, which of the following graphs shows the variation of the kinetic energy of the stone with the distance travelled during its upward motion? 25. Which of the following is a correct unit for the corresponding physical quantity? Physical quantity Unit A. Work watt B. Upthrust (Out of Syllabus) kilogram C. Momentum newton second D. Heat Capacity joule per kilogram E. Electromotive force newton 26. Two blocks X and Y are connected by a light string passing over a smooth pulley as shown above. The mass of X is greater than that of Y. The two blocks are released from rest. Which of the following statements is/are correct? 24. Which of the following pairs of physical quantities has the same units? A. Charge and current B. Frequency and time C. Kinetic energy and heat D. Moment and momentum E. Work and potential difference (1) The potential energy lost by X is equal to the potential energy gained by Y. (2) The kinetic energy gained by X is greater than the kinetic energy gained by Y. (3) The potential energy lost by X is equal to the sum of kinetic energies gained by X and Y. A. (2) only D. (1) and (3) only
Physics-MC 2006-7 Page 27 of 29 27. Figure (a) Figure(b) 29. A motor car of mass 2500 kg accelerates from rest to a speed of 20 m s 1 in 5 s on a level road. Find the average power of the car. A. 10 kw B. 50 kw C. 100 kw D. 200 kw E. 250 kw 28. A bullet of mass 0.02 kg travelling at 450 m s 1 enters a wooden block as shown in Figure (a) and leaves it with a speed 400 m s 1. In Figure (b), what is the maximum number of identical blocks that the same bullet can pass through? A. 3 B. 4 C. 5 D. 9 E. 10 A trolley runs down a friction-compensated runway as shown above. Which of the following statements is true? A. The kinetic energy of the trolley increases with time. B. The potential energy of the trolley increases with time. C. The sum of kinetic and potential energies of the trolley remains unchanged. D. The frictional force acting on the trolley is zero. E. The resultant force acting on the trolley is zero. 30. Which of the following physical quantities is not a vector? A. Acceleration B. Momentum C. Velocity D. Weight E. Work 31. A particle of mass m is thrown vertically upwards with initial speed v. When the particle returns to its starting point, what are the changes in momentum and kinetic energy of the particle? Change in momentum Change in kinetic energy A. 0 0 B. 0 mv 2 C. mv 1 2 mv2 D. 2mv 0 E. 2mv mv 2
Physics-MC 2006-7 Page 28 of 29 32. 33. Which of the following units does not represent energy? A. J B. N m C. W s D. Pa m 3 E. kg m s 2 34. A pendulum bob is suspended by a light inextensible string. The bob is released from rest at a point A as shown above. When the bob reaches the lowest point B, the string hits a fixed pin. Which of the following statements is/are correct? (1) The bob has maximum kinetic energy at B. (2) The highest level that the bob can reach is the level of the pin. (3) The work done by the tension of the string is zero throughout the motion. A. (2) only D. (1) and (3) only A man pulls a 50 kg block up a smooth inclined plane making an angle 30 with the horizontal as shown above. The inclined plane is 6 m long and the block is pulled from the bottom of the inclined plane to the top in 30 s. Find the average useful output power of the man. A. 5 W B. 10 W C. 50 W D. 87 W E. 100 W
Physics-MC 2006-7 Page 29 of 29 Momentum 1. Which of the following is/are correct unit(s) for momentum? (1) kg m s 1 (2) kg m s 2 (3) N s B. (2) only C. (3) only D. (1) and (3) only E. (2) and (3) only 2. Bullets, each of mass m, are fired at the rate of n bullets per second. They hit a vertical wall with horizontal speed v and rebound from the wall with the same horizontal speed v. Which of the following statements is/are correct? (1) The total change in momentum of the bullets is zero. (2) The total change in momentum of the bullets in one second is 2mnv. (3) The average force exerted on the wall is 2mnv. B. (2) only C. (3) only D. (1) and (3) only E. (2) and (3) only 3. A block is pulled by a constant force and moves along a smooth horizontal surface. Which of the following describes the variations of the acceleration and momentum of the block during the time when the force is acting? 4. Acceleration Momentum A. remains unchanged remains unchanged B. remains unchanged increases C. increases remains unchanged D. increases increases E. decreases increases Two particles A and B of masses 2 kg and 1 kg respectively move in opposite directions. The initial velocity of A is 4 m s 1 towards the right, while that of B is 2 m s 1 towards the left. They collide head on. After the collision, the velocity of A becomes 1 m s 1 towards the RIGHT. What would be the velocity of particle B? ( A. 2 m s 1 towards the right B. 3 m s 1 towards the right C. 4 m s 1 towards the right D. 6 m s 1 towards the right E. 7 m s 1 towards the right