Newton's Second Law and Momentum/Impulse — Practice Questions

Free NEET Physics multiple-choice questions on Newton's Second Law and Momentum/Impulse. Attempt each question and reveal the answer with a full explanation.

A body of mass M hits a wall normally with velocity v and bounces back with the same velocity. The change in momentum is: 2Mv -Mv zero Mv A man of mass 60 kg is standing on a weighing scale in a lift which is moving down with an acceleration of 10 m/s 2 . The reading of the weighing scale will be: ( g = 10 m/s 2 ) 0 N 600 N 1200 N 60 N A machine gun fires 10 bullets per second, each of mass 20 g, with a velocity of 500 m/s. The force required to hold the gun in position is: 100 N 10 N 50 N 200 N A block of mass m is placed on a smooth horizontal surface. A force F is applied at an angle with the horizontal. The acceleration of the block is: F / m F / m F / m (F - mg) / m Two blocks of masses 7 kg and 5 kg are placed in contact with each other on a smooth horizontal surface. A force of 6 N is applied on the 7 kg block. The force on the 5 kg block is: 2.5 N 3.5 N 6 N 5 N A person is standing on a weighing machine in a lift. In which case will the machine show the maximum reading? Lift moving upwards with uniform acceleration Lift moving downwards with uniform acceleration Lift moving upwards with uniform velocity Lift moving downwards with uniform velocity A ball of mass m is moving with speed v and strikes a wall normally and rebounds with speed v . The change in kinetic energy is: 0 mv 2 1/2 mv 2 2mv 2 A man of mass 70 kg stands on a weighing scale in a lift which is moving downwards with a uniform acceleration of 5 m/s 2 . The reading on the scale is: ( g = 10 m/s 2 ) 350 N 700 N 1050 N 70 N A ball of mass m falls vertically and hits the ground with speed v 1 and bounces back vertically with speed v 2 . The change in momentum is: m(v 1 + v 2) m(v 1 - v 2) m(v 2 - v 1) 0 Sand is being dropped on a conveyor belt at the rate of M kg/s. The force necessary to keep the belt moving with a constant velocity of v m/s is: Mv Mv / 2 zero 2Mv The force on a rocket moving with a velocity 300 m/s is 210 N. The rate at which the fuel is being burnt is: 0.7 kg/s 1.4 kg/s 0.07 kg/s 10.7 kg/s If the force on a rocket, which is ejecting gases with a relative velocity of 600 m/s, is 210 N, then the rate of combustion of the fuel is: 0.35 kg/s 0.7 kg/s 1.4 kg/s 10.5 kg/s A block of mass m is connected to another block of mass M by a spring (spring constant k ). A constant force F acts on block M . The acceleration of the center of mass of the system is: F / (m + M) F / M F / m Zero A lift is descending with an acceleration a . The apparent weight of a body of mass m in the lift is its real weight reduced by: ma mg m(g-a) m(g+a) A constant force acting on a body of mass 3 kg changes its speed from 2 m/s to 3.5 m/s in 25 s. The direction of motion of the body remains unchanged. What is the magnitude of the force? 0.18 N 0.36 N 0.9 N Zero An object of mass 10 kg is suspended by a string. If it is accelerated upwards with 2 m/s 2 and then downwards with 2 m/s 2 , the ratio of the tensions in the string in the two cases is: ( g = 10 m/s 2 ) 3 : 2 2 : 3 5 : 4 4 : 5 A bullet of mass m hits a target with velocity v and comes to rest in it. If the target is a large block of wood of mass M free to move on a smooth surface, the velocity of the block after impact is: mv / (M + m) mv / M Mv / (M + m) (M + m)v / m A body of mass 2 kg is acted upon by two forces 3 N and 4 N perpendicular to each other. The magnitude of acceleration is: 2.5 m/s 2 3.5 m/s 2 5.0 m/s 2 1.5 m/s 2 The force on a particle is F = kx , where k is a positive constant and x is the displacement. The motion of the particle is: Accelerated Uniform Decelerated Simple Harmonic 300 J of work is done in sliding a 2 kg block up an inclined plane of height 10m. Taking g = 10 m/s 2 , work done against friction is 200 J 100 J Zero 1000 J A block B is pushed momentarily along a horizontal surface with an initial velocity V. If is the coefficient of sliding friction between B and the surface, block B will come to rest after a time g /V V/g V/g V/(g ) . Which one of the following statements is incorrect? Frictional force opposes the relative motion. Limiting value of static friction is directly proportional to normal reaction. Rolling friction is smaller than sliding friction. Coefficient of sliding friction has dimensions of length. A cricketer catches a ball of mass 150 g in 0.1 s moving with a speed of 20 m/s. Then he experiences a force of: 30 N 3 N 300 N 0.3 N Calculate the maximum acceleration of a moving car so that a body lying on the floor of the car remains stationary. The coefficient of static friction between the body and the floor is 0.15 (g = 10 m s -2 ) . 1.2 m s -2 150 m s -2 1.5 m s -2 50 m s -2 There are two inclined surfaces of equal length (L) and same angle of inclination 45 with the horizontal. One of them is rough and the other is perfectly smooth. A given body takes 2 times as much time to slide down on rough surface than on the smooth surface. The coefficient of kinetic friction ( k) between the object and the rough surface is close to 0.75 0.25 0.40 0.5 A box of mass 15 kg is kept on the floor of a stationary trolley. The coefficient of static friction between the box and the trolley is 0.12 . Keeping the box in stationary state over the trolley, the maximum acceleration with which the trolley can be moved horizontally in m s -2 is: ( g = 10 m/s 2 ) 1.8 1.2 1.5 2.1 A block of mass m is placed on a truck moving with an acceleration a . The force of friction acting on the block if it does not slip relative to the truck is: ma mg m(g+a) Zero A force-time ( F-t ) graph for a particle of mass 2 kg is shown as an isosceles triangle with a base of 4 s and a peak height of 10 N at t=2 s. The final velocity of the particle starting from rest is: 10 m/s 20 m/s 5 m/s 40 m/s A mass of M kg is suspended by a weightless string. The horizontal force required to hold the mass at 60 with the vertical is: Mg 3 Mg/ 3 Mg Mg/2 A light string passing over a smooth light pulley connects two blocks of masses m 1 and m 2 ( m 1 > m 2 ). If the acceleration of the system is g/8 , then the ratio m 1/m 2 is: 9/7 8/1 4/3 5/3 A bullet fired from a gun experiences a force F = 50 - 10 4 t (in N) till it leaves the barrel. If the time taken to leave the barrel is 5 ms, the impulse imparted is: 0.125 Ns 0.25 Ns 0.5 Ns 1.0 Ns An object of mass 10 kg moves at a constant speed of 10 m/s. A constant force, that acts for 4 seconds on the object, gives it a speed of 2 m/s in opposite direction. The force acting on the object is: -30 N -20 N 30 N 20 N A jet of water with cross-section area A and velocity v strikes a wall normally and stops. The force exerted by the water on the wall is: A v 2 A v 1 2 A v 2 A v 3 A bullet of mass 10 g is fired from a gun of mass 5 kg with a muzzle velocity of 400 m/s. The recoil velocity of the gun is: 0.8 m/s 8 m/s 0.4 m/s 4 m/s A bullet of mass 10 g moving with a velocity of 100 m/s hits a wooden block and penetrates 5 cm before coming to rest. The average force exerted by the block on the bullet is: 1000 N 100 N 500 N 2000 N Three blocks are connected on a horizontal frictionless table by two strings. The masses are m 1 = 1 kg, m 2 = 2 kg, and m 3 = 3 kg. A force of 12 N is applied on m 3 . The tension in the string between m 1 and m 2 is: 2 N 4 N 6 N 1 N The force F on a particle varies with time t as F = at + bt 2 . The change in momentum of the particle between t=1 s and t=2 s is: 3a/2 + 7b/3 a + b 2a + 4b 3a/2 + b A constant force F = m 2 g / 2 is applied on the block m 1 as shown. The string and pulley are massless and frictionless. The acceleration of the system is: g(2m 2 - m 1) 2(m 1 + m 2) g(m 2 - m 1) m 1 + m 2 g 2 g(m 2 + m 1) 2(m 1 - m 2) A rigid ball of mass m strikes a rigid wall at an angle of 30 with the wall and gets reflected without loss of speed v . The value of impulse imparted by the wall on the ball will be: mv 3 mv 2mv mv/2 Three blocks A, B and C of masses 4 kg, 2 kg and 1 kg respectively, are in contact on a frictionless surface. If a force of 14 N is applied on the 4 kg block, then the contact force between A and B is: 6 N 8 N 18 N 2 N A 0.5 kg ball moving with a speed of 12 m/s strikes a hard wall at an angle of 30 with the wall. It is reflected with the same speed and at the same angle. If the ball is in contact with the wall for 0.25 s, the average force acting on the wall is: 24 N 48 N 12 N 96 N A uniform string of length L and mass M is lying on a smooth table and 1/3 of its length is hanging vertically down over the edge of the table. If g is the acceleration due to gravity, the work required to pull the hanging part on the table is: MgL/18 MgL/6 MgL/9 MgL/3 A 100 kg gun fires a ball of 1 kg 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: 0.4 m/s 0.2 m/s 4 m/s 0.1 m/s A body of mass 2 kg moving with a velocity of (3 i + 4 j ) m/s is acted upon by a constant force of ( i - 2 j ) N. The velocity of the body after 4 s will be: (5 i j ) m/s (5 i + 4 j ) m/s (3 i - 4 j ) m/s (2 i + 2 j ) m/s A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the bag reads 49 N when the lift is stationary. If the lift moves downward with an acceleration of 5 m/s 2 , the reading of the spring balance will be: ( g = 9.8 m/s 2 ) 24 N 49 N 74 N 15 N A bullet of mass 10 g is fired from a gun of mass 5 kg. If the muzzle velocity is 500 m/s, the kinetic energy of the recoil of the gun is: 2.5 J 5 J 1.25 J 10 J A mass of 1 kg is suspended by a string. It is lifted up with an acceleration 4.9 m/s 2 and then lowered with an acceleration 4.9 m/s 2 . The ratio of the tensions in the two cases is: ( g = 9.8 m/s 2 ) 3 : 1 2 : 1 1 : 3 1 : 2 A force F = (5 + 3t) N acts on a particle of mass 2 kg initially at rest. The velocity of the particle after 10 s will be: 100 m/s 50 m/s 150 m/s 200 m/s A block of mass M is pulled by a force F on a smooth horizontal surface. A mass m is connected to it by a string. If the tension in the string is T , then T is: mF / (M + m) MF / (M + m) F (M + m)F / m A bomb of mass 30 kg at rest explodes into two pieces of masses 18 kg and 12 kg. The velocity of 18 kg mass is 6 m/s. The kinetic energy of the other mass is: 486 J 524 J 256 J 324 J A body of mass 2 kg is moving in the x-y plane. Its momentum is given by p = 2 (t) i + 2 (t) j . The force acting on the body is: 2 (t) i - 2 (t) j -2 (t) i + 2 (t) j 2 (t) i + 2 (t) j Zero A block of mass m is placed on a smooth wedge of inclination . The wedge is moved with an acceleration a such that the block remains stationary relative to the wedge. The value of a is: g g g g The tension in a string holding a 5 kg mass in a lift is 60 N. The acceleration of the lift is: ( g = 10 m/s 2 ) 2 m/s 2 upwards 2 m/s 2 downwards 12 m/s 2 upwards Zero A ball of mass 0.5 kg is moving with velocity 2 m/s. It strikes a wall and bounces back with the same speed in 0.1 s. The average force exerted by the wall is: 20 N 10 N 5 N 40 N Two masses m 1 = 1 kg and m 2 = 2 kg are connected by a string. If the system is pulled by a force of 6 N on the 2 kg mass on a smooth surface, the tension in the string is: 2 N 4 N 6 N 3 N A body of mass 2 kg is moving with a velocity of 10 m/s. A force is applied for 4 s in the direction of motion. The force-time graph is a rectangle of height 5 N. The final velocity of the body is: 20 m/s 10 m/s 15 m/s 25 m/s A block of mass m is placed on a smooth inclined wedge ABC of inclination as shown in the figure. The wedge is given an acceleration a towards the right. The relation between a and for the block to remain stationary relative to the wedge is: a = g a = g a = g / a = g A rigid ball of mass m strikes a rigid wall at 60 and gets reflected without loss of speed as shown in the figure. The value of impulse imparted by the wall on the ball will be: mv mv / 2 2mv mv / 2 The force F acting on a particle of mass m is indicated by the force-time graph shown below. The change in momentum of the particle over the time interval from 0 to 8 s is: 24 Ns 20 Ns 12 Ns 6 Ns An object of mass 3 kg is at rest. Now a force of F = 6t 2 i + 4t j is applied on the object. The velocity of the object at t = 3 s is: 18 i + 6 j 18 i + 3 j 9 i + 6 j 12 i + 8 j A monkey of mass 20 kg is holding a vertical rope. The rope will not break when a mass of 25 kg is suspended from it but will break if the mass exceeds 25 kg. What is the maximum acceleration with which the monkey can climb up along the rope? ( g = 10 m/s 2 ) 2.5 m/s 2 5 m/s 2 10 m/s 2 1.25 m/s 2 A block of mass M is pulled along a horizontal frictionless surface by a rope of mass m . If a force F is applied at the free end of the rope, the net force exerted on the block is: FM / (M + m) F Fm / (M + m) F(M + m) / M Three blocks of masses m 1 , m 2 and m 3 are placed in contact on a smooth horizontal surface. A horizontal force F is applied to m 1 . The contact force between m 2 and m 3 is: m 3 F m 1 + m 2 + m 3 m 1 F m 1 + m 2 + m 3 (m 2 + m 3) F m 1 + m 2 + m 3 m 2 F m 1 + m 2 + m 3 A force F = 6 i - 8 j + 10 k N produces an acceleration of 1 m/s 2 in a body. The mass of the body in kg is: 10 2 10 20 6 2 A body of mass 0.4 kg is moving with a constant speed of 10 m/s along the north. A force of 8 N is applied towards the south for 2 s. The final velocity of the body is: 30 m/s towards south 30 m/s towards north 50 m/s towards south 10 m/s towards north A bomb of mass 9 kg explodes into two pieces of masses 3 kg and 6 kg. The velocity of the 3 kg piece is 1.6 m/s. The kinetic energy of the 6 kg piece is: 1.92 J 3.84 J 0.96 J 7.68 J A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration 1.0 m/s 2 . If g = 10 m/s 2 , the tension in the supporting cable is: 11000 N 1100 N 1200 N 8600 N A heavy uniform chain of length L and mass M is hanging vertically from a support. The tension in the chain at a distance x from the lower end is: (Mg/L)x (Mg/L)(L - x) Mg (Mg/L)(L + x) A particle of mass m is moving with velocity v and it strikes a wall and rebounds with the same speed. If the angle of incidence is 45 with the normal, the magnitude of change in momentum is: 2 mv 2 mv mv mv / 2 A body of mass 3 kg hits a wall at an angle of 30 with the wall and rebounds with the same speed of 10 m/s. The change in momentum of the body is: 30 kg m/s 60 kg m/s 30 3 kg m/s 0 kg m/s A bullet of mass 0.04 kg moving with a speed of 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: 270 N 180 N 450 N 540 N The upper half of an inclined plane of inclination is perfectly smooth while lower half is rough. A block starting from rest at the top of the plane will again come to rest at the bottom, if the coefficient of friction between the block and lower half of the plane is given by = 1 = 2 =2 = A system consists of three masses m 1 , m 2 and m 3 connected by a string passing over a pulley P. The mass m 1 hangs freely and m 2 and m 3 are on a rough horizontal table (the coefficient of friction = ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m 1 is : (Assume m 1 = m 2 = m 3 = m ) g(1-3 ) 9 2g 3 g(1-2 ) 3 g(1-2 ) 2 A girl jumps down from a moving bus, along the direction of motion of the bus, tilting slightly forward. She falls on (a) a sheet of ice (b) a patch of glue. In case (a) she falls backward and in case (b) she falls forward In both cases (a) and (b) she falls forward In both cases (a) and (b) she falls backward In case (a) she falls forward and in case (b) she falls backward A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to keep the block stationary when the cylinder is vertical and rotating about its axis, will be : ( g=10 m/s 2 ) 10 rad/s 10 rad/s 10 2 rad/s 10 rad/s A uniform rod of mass 20 kg and length 5 m leans against a smooth vertical wall making an angle of 60 with it. The other end rests on a rough horizontal floor. The friction force that the floor exerts on the rod is (Take g = 10 m/s 2 ) 200 3 N 100 N 100 3 N 200 N A bullet is fired from a gun. The force on the bullet is given by F = 600 - 2 10 5 t , where F is in newtons and t in seconds. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet? 0.9 Ns 1.8 Ns 2.4 Ns 0.3 Ns A bullet of mass a and velocity b is fired into a large block of mass c . The final velocity of the system is: ab a + c cb a + c ab c a+b c A system consists of three masses m 1, m 2 and m 3 connected by a string passing over a pulley P . The mass m 1 hangs freely and m 2 and m 3 are on a rough horizontal table (the coefficient of friction is ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m 1 is: (Assume m 1 = m 2 = m 3 = m ) g(1 - 2 ) / 3 g(1 - ) / 3 g(1 - 2 ) / 2 g(1 - ) / 2 A 1 kg stationary bomb explodes into three fragments having mass ratio 1:1:3 . The fragments with equal mass fly off in mutually perpendicular directions with velocity 30 m/s each. The velocity of the third fragment is: 10 2 m/s 10 m/s 30 2 m/s 15 m/s A balloon with mass M is descending down with an acceleration a (where a < g ). How much mass should be removed from it so that it starts moving up with an acceleration a ? 2Ma / (g + a) 2Ma / (g - a) Ma / (g + a) Ma / (g - a) A block A of mass m 1 rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block B of mass m 2 is suspended. The coefficient of kinetic friction between the block and the table is k . When the blocks are in motion, the tension in the string is: m 1 m 2 (1 + k) g m 1 + m 2 m 1 m 2 (1 - k) g m 1 + m 2 (m 2 - k m 1) g m 1 + m 2 m 1 m 2 g m 1 + m 2 Two masses M and m are attached to a vertical spring as shown. When the system is in equilibrium and the lower mass m is removed, the upper mass M starts oscillating. The amplitude of oscillation is: mg/k Mg/k (M+m)g/k (M-m)g/k Two blocks A and B of masses 2m and m are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in the figure. The magnitude of acceleration of A and B immediately after the string is cut, are respectively: g/2, g g, g g, g/2 g/2, g/2 A block of mass m is placed on a smooth wedge of inclination . The whole system is accelerated horizontally so that the block does not slip on the wedge. The normal reaction of the wedge on the block is: mg / mg mg mg A heavy uniform rope of length L and mass M is pulled by a constant force F on a smooth horizontal surface. The tension in the rope at a distance x from the end where the force is applied is: F(1 - x/L) Fx/L F F(L/x) An object of mass 5 kg is acted upon by a force F = (-3 i + 4 j ) N. If its initial velocity at t=0 is v = (6 i - 12 j ) m/s, the time at which it will just have a velocity along the y-axis is: 10 s 5 s 2 s 15 s A smooth sphere of radius R is made to translate in a straight line with a constant acceleration a . A particle kept on the top of the sphere is released from there at zero velocity with respect to the sphere. The particle slides down the sphere and leaves the surface at an angular position with the vertical. The value of depends on: both a and g only g only a neither a nor g A shell of mass 200 g is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 80 m/s, then the recoil speed of the gun is: 16 cm/s 1.6 m/s 8 cm/s 0.8 m/s A block of mass m is placed on a smooth wedge of inclination . The wedge is given an acceleration a horizontally so that the block does not slip. The work done by the net force on the block as observed from the ground in time t is: 1 2 m (g ) 2 t 2 1 2 m g 2 t 2 m g a t Zero A block of mass m is resting on a smooth horizontal surface. One end of a uniform rope of mass m/3 is fixed to the block. A force F is applied to the other end of the rope. The tension at the middle of the rope is: 7F/8 F/8 F/4 3F/4 Two blocks A and B of masses 2 kg and 3 kg respectively are connected by a light string passing over a frictionless pulley. If the system is released from rest, the acceleration of the center of mass of the system is: g/25 g/5 g/10 g/15 A man of mass m is standing on a plank of mass M kept on a smooth surface. If the man starts moving on the plank with velocity v relative to the plank, the velocity of the plank relative to the ground is: mv / (M + m) Mv / (M + m) v mv / M