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Class 11 Physics Objective Chapter – 5 Law of Motion
1. A machine gun has a mass 5 kg. It fires 50 gram bullets at the rate of 30 bullets per minute at a speed of 400 ms–1. What force is required to keep the gun in position
(a) 10 N
(b) 5 N
(c) 15 N
(d) 30 N
Ans:- (a)
2. What is the formula to find linear velocity?
( a ) Linear velocity = 2(Mass + Velocity)
( b ) Linear velocity = Mass / Velocity
( c ) Linear velocity = Mass * Velocity
( d ) Linear velocity = Mass – Velocity
Ans:- (c)
3. A uniform rope of length L resting on a frictionless horizontal surface is pulled at one end by a force F. What is the tension in the rope at a distance l from the end where the force is applied.
( a ) F
( b ) F (1 + l/L)
( c ) F/2
( d ) F (1 – l/L)
Ans:- (d)
4. An aircraft executes a horizontal loop at a speed of 720 km/h with its wings banked at 15°. What is the radius of the loop?
( a ) 15 km
( b ) 23.567 m
( c ) 12.781 m
( d ) 14 km
Ans:- (a)
5. The inherent property, with which a body resists any change in its state of motion is known as ———————–
( a ) Force
( b ) Momentum
( c ) Inertia
( d ) Acceleration
Ans:- (c)
6. An object at rest in space suddenly explodes into three parts of same mass. The momentum of the two parts are 2p SHAPE \* MERGEFORMAT and p SHAPE \* MERGEFORMAT . The momentum of the third part
( a ) will have a magnitude p√3
( b ) will have a magnitude p√ 5
( c ) will have a magnitude p
( d ) will have a magnitude 2p.
Ans:-(b)
7. 1 Newton = ————–
( a ) 1 Newton = 1 kg x 1 m/s2
( b ) 1 Newton = 1 kg
( c ) 1 Newton = 1 kg x 1 m/s
( d ) 1 Newton = m/s2
Ans:- (a)
8. Newton’s first law of motion describes the
( a ) inertia
( b ) energy
( c ) work
( d ) moment of inertia
Ans:- (a)
9. Inertia is the property of a body linked to tendency of a body
( a ) to resist any change in its state
( b ) to change the momentum
( c ) to change its direction
( d ) to change its position
Ans:- (a)
10. Physical independence of force is a consequence of
( a ) first law of motion
( b ) third law of motion
( c ) second law of motion
( d ) all of these
Ans:- (a)
11. A rocket of mass 5000 kg is to be projected vertically upward. The gases are exhausted vertically downwards with velocity 1000 ms–2 with respect to the rocket. What is the minimum rate of burning the fuel so as to just lift the rocket upwards against gravitational attraction
(a) 49 kg s–1
(b) 147 kg s–1
(c) 98 kg s–1
(d) 196 kg s–1
Ans:- (a)
12. When an elevator cabin falls down, the cabin and all the bodies fixed in the cabin are accelerated with respect to
(a) man standing on earth
(b) ceiling of elevator
(c) floor of elevator
(d) man standing in the cabin
Ans:- (a)
13. If the net external force on the body is zero, its
( a ) Speed is zero
( b ) Acceleration is zero
( c ) Displacement is zero
( d ) Velocity is zero
Ans:- (b)
14. The direction of impulse is
( a ) same as that of the net force
( b ) opposite to that of the net force
( c ) same as that of the final velocity
( d ) same as that of the initial velocity
Ans:- (a)
15. A player stops a football weighting 0.5 kg which comes flying towards him with a velocity of 10m/s. If the impact lasts for 1/50th sec. and the ball bounces back with a velocity of 15 m/s, then the average force involved is
( a ) 250 N
( b ) 1250 N
( c ) 500 N
( d ) 625 N
Ans:- (d)
16. When a bull pulls a cart, the force that helps the bull to move forward is the force exerted by
( a ) the ground on the bull
( b ) the cart on the bull
( c ) the bull on the ground
( d ) the ground on the cart
Ans:- (a)
17. When a body is stationary
( a ) the combination of forces acting on it balances each other
( b ) the body is in vacuum
( c ) the force acting on it is not in contact with it
( d ) there is no force acting on it
Ans:- (a)
18. A machine gun fires a bullet of mass 40 g with a velocity of 1200 ms-1. The man holding it can exert a maximum force on 144 N on the gum. How many bullets can he fire per second at the most?
( a ) one
( b ) four
( c ) two
( d ) three
Ans:- (d)
19. Dust can be removed out of a blanket using
( a ) Law of inertia
( b ) Newton’s second law of motion
( c ) Newton’s third law of motion
( d ) Newton’s law of gravitation
Ans:- (a)
20. A block of wood is placed on a surface. A force is applied parallel to the surface to move the body. The frictional force developed acts
( a ) normal to the surface upwards
( b ) normal to the surface downwards
( c ) along the direction of the applied force
( d ) opposite to the direction of the applied force
Ans:- (d)
21. A monkey is climbing up a rope, then the tension in the rope
( a ) must be equal to the force applied by the monkey on the rope
( b ) must be less than the force applied by the monkey on the rope.
( c ) must be greater than the force applied by the monkey on the rope.
( d ) may be equal to, less than or greater the force applied by the monkey on the rope.
Ans:- (a)
22. A body of mass 4 kg moving on a horizontal surface with an initial velocity of 6 ms–1 comes to rest after 3 seconds. If one wants to keep the body moving on the same surface with the velocity of 6 ms–1, the force required is
( a ) Zero
( b ) 4 N
( c ) 8 N
( d ) 16 N
Ans:- (c)
23. The mass of a body which is equal to the ratio of the force acting on a body to the acceleration produced in the body is
( a ) the gravitational mass
( b ) the electromagnetic mass
( c ) the internal mass
( d ) the inertial mass
Ans:- (d)
24. Which law governs the phenomenon that a tablecloth is pulled out from under a setting of chinaware without damaging it?
( a ) Newton’s first law
( b ) Universal law of gravitation
( c ) Newton’s second law
( d ) Newton’s third law
Ans:- (a)
25. The force required to produce an acceleration of 2 m/s² on a mass of 2 kg is
( a ) 4 N
( b ) 10 N
( c ) 22 N
( d ) 18 N
Ans:- (a)
26. Two masses are in the ratio 1:5. What is ratio of their inertia?
( a ) 1 : 5
( b ) 5 : 1
( c ) 1 : 25
( d ) 25 : 1
Ans:- (c)
27. A passenger sitting in a bus moving at uniform speed, feels pushed backward whenever the bus is accelerated forward. This type of force is called
( a ) Gravitational force
( b ) real force
( c ) fictitious force or pseudo force
( d ) frictional force
Ans:- (c)
28. How is inertia used when riding a bicycle?
( a ) Bicycles don’t use inertia.
( b ) You can stop paddling and still continue rolling forward
( c ) You must paddle harder when going up hill.
( d ) You must paddle slower when going up hill.
Ans:- (b)
29. We slip on a rainy day due to
( a ) Change in momentum
( b ) Inertia
( c ) Decrease in friction
( d ) Increase in friction
Ans:- (c)
30. A spherical ball of mass 10-6 kg hits a wall 1000 times per second normally with a velocity of 1000 m/s and rebounds with same velocity along the initial direction. The force experienced by the wall is
( a ) 1 N
( b ) 4 N
( c ) 2 N
( d ) 8 N
Ans:- (c)
31. Two blocks of masses 2 kg and 1 kg are placed on a smooth horizontal table in contact with each other. A horizontal force of 3 newton is applied on the first so that the block moves with a constant acceleration. The force between the blocks would be
( a ) 3 newton
( b ) 2 newton
( c ) 1 newton
( d ) zero
Ans:- (c)
32. A reference frame attached to the earth
( a ) cannot be an inertial frame because earth is revolving round the sun
( b ) is an inertial frame by definition
( c ) is an inertial frame because Newton’s laws are applicable
( d ) is an inertial frame because the earth is rotating about its own axis
Ans:- (a)
33. A body of mass 5 kg is travelling with a uniform velocity of 2 m/s. Its momentum is
( a ) 10 kg m/s
( b ) 7 kg m/s
( c ) 2 .5 kg m/s
( d ) 3 kg m/s
Ans:- (a)
34. A particle of mass m moving eastward with a speed v collides with another particle of the same mass moving northward with the same speed v. The two particles coalesce on collision. The new particle of mass 2m will move in the north external direction with a velocity
( a ) v/2
( b ) 2v
( c ) v / 2
( d ) None of these
Ans:- (c)
35. Which is the branch of physics that deals with the motion of a body by considering the cause?
( a ) Statics
( b ) Thermodynamics
( c ) Dynamics
( d ) Astronomy
Ans:- (c)
36. A body of mass 5 kg is travelling with a uniform velocity of 2 m/s. Its momentum is
( a ) 10 kg m/s
( b ) 7 kg m/s
( c ) 2 .5 kg m/s
( d ) 3 kg m/s
Ans:- (a)
37. A 50 kg ice skater, initially at rest, throws a 0.15 kg snowball with a speed of 35 m/s. What is the approximate recoil speed of the skater
( a ) 0.10 m/s
( b ) 0.20 m/s
( c ) 0.70 m/s
( d ) 1.4 m/s
Ans:- (a)
38. Passengers in a bus lean forward as bus suddenly stops. This is due to
( a ) Impulse
( b ) Change in speed
( c ) Inertia
( d ) Change in momentum
Ans:- (c)
39. A gun of mass 1000 kg fires a projectile of mass 1 kg with a horizontal velocity of 100 m/s. The velocity of recoil of the gun in the horizontal direction is
( a ) 5 m/s
( b ) 0.1 m/s
( c ) 15 m/s
( d ) 20 m/s
Ans:- (b)
40. When external force is not applied to the system, its total momentum ———–
( a ) Becomes zero
( b ) Remains constant
( c ) Increases gradually
( d ) Decreases gradually
Ans:- (b)
41. Centripetal force :
( a ) can change speed of the body.
( b ) is always perpendicular to direction of motion
( c ) is constant for uniform circular motion.
( d ) all of these
Ans:- (b)
42. Inside the nucleus, two protons are held together by a force which overcomes the repulsion. This force is called
( a ) gravitational force
( b ) electrostatic force
( c ) weak force
( d ) strong force
Ans:- (d)
43. When a horse pulls a cart, the horse moves down to (a) horse on the cart.
( b ) cart on the horse.
( c ) horse on the earth.
( d ) earth on the horse.
Ans:- (d)
44. A 4000 kg lift is accelerating upwards. The tension in the supporting cable is 48000 N. If g = 10ms-2 then the acceleration of the lift is
( a ) 1 ms-2
( b ) 2 ms-2
( c ) 4 ms-2
( d ) 6 ms-2
Ans:- (b)
45. A rocket has a mass of 100 kg. Ninety percent of this is fuel. It ,ejects fuel vapors at the rate of 1 kg/sec with a velocity of 500 m/sec relative to the rocket. It is supposed that the rocket is outside the gravitational field. The initial upthrust on the rocket when it just starts moving upwards is
( a ) zero
( b ) 500 newton
( c ) 1000 newton
( d ) 2000 newton
Ans:- (b)
46. A 0.1 kg block suspended from a massless string is moved first vertically up with an acceleration of 5ms-2 and then moved vertically down with an acceleration of 5ms-2 . If T1 and T2 are the respective tensions in the two cases, then
( a ) T2 > T1
( b ) T1 – T2 = 1 N, if g = 10ms-2
( c ) T1 -T2 = 1kg f
( d ) T1 – T2 = 9.8N, if g = 9.8 ms-2
Ans:- (b)
47. A body is sliding down a rough inclined plane which makes an angle of 30 degree with the horizontal. If the coeffcient of friction is 0.26, the acceleration in m/s² is
( a ) 1.95
( b ) 2.78
( c ) 3.47
( d ) 4.6
Ans:- (b)
48. Which law is in control of a spacecraft that cruises through space at a constant speed without using any fuel?
( a ) Universal law of gravitation
( b ) Newton’s third law
( c ) Newton’s second law
( d ) Newton’s first law
Ans:- (d)
49. What is the net force of a kite that is held stationary in the sky?
( a ) 1
( b ) Increasing
( c ) 0
( d ) Decreasing
Ans:- (b)
50. The force of action and reaction
( a ) must be of same nature
( b ) must be of different nature
( c ) may be of different nature
( d ) may not have equal magnitude
Ans:- (a)
51. A bullet of mass 25 g moving with a velocity of 200 cm/s is stopped within 5 cm of the target. The average resistance offered by the target is
( a ) 1 N
( b ) 2 N
( c ) 3 N
( d ) 4 N
Ans:- (a)
52. A mass is hanging on a spring balance which is kept in a lift The lift ascends. The spring balance will show in its readings
( a ) an increase
( b ) a decrease
( c ) no change
( d ) a change depending on its velocity
Ans:- (a)
53. A spring is compressed between two toy carts of mass m1 and m2. When the toy carts are released, the springs exert equal and opposite average forces for the same time on each toy cart. If v1 and v2 are the velocities of the toy carts and there is no friction between the toy carts and the ground, then:
( a ) v1/v2 = m1/m2
( b ) v1/v2 = m2/m1
( c ) v1/v2 = –m2/m1
( d ) v1/v2 = –m1/m2
Ans:- (c)
54. A rider on a horse back falls forward when the horse suddenly stops. This is due to
( a ) inertia of horse
( b ) inertia of rider
( c ) large weight of the horse
( d ) losing of the balance
Ans:- (b)
55. The variation of force F acting on a body moving along x-axis varies with its position (x) shown in figure. The body is in stable equilibrium state at
( a ) P
( b ) Q
( c ) R
( d ) both P & Q
Ans:- (b)
56. A ball of mass m is thrown vertically upwards. What is the rate at which the momentum of the ball changes
( a ) Zero
( b ) mg
( c ) Infinity
( d ) Data is not sufficient
Ans:- (b)
57. A weight W rests on a rough horizontal plane. If the angle of friction be q , the least force that will move the body along the plane will be
( a ) Wcosq
( b ) Wcotq
( c ) Wtanq
( d ) Wsinq
Ans:- (c)
58. A bird is in a wire cage which is hanging from a spring balance . In the first case, the bird sits in the cage and in the second case, the bird flies about inside the cage. The reading in the spring balance is
( a ) more in the first case
( b ) less in first case
( c ) unchanged
( d ) zero in second case
Ans:- (a)
59. A 10 kg block is pulled a along a frictional surface in the form of an are of a circle of radius 10 m. The applied force F is 200 N as shown in figure If a block started from rest at P
( a ) the velocity at Q would be 20 m/s
( b ) the velocity at Q would be 17 m/s
( c ) the velocity at Q would be 15 .5 m.s
( d ) the velocity at Q would be 18 m/s
Ans:- (a)
60. If two masses (M & m) are connected on a horizontal plane and a force is applied on the combination, then the tension T depends on
( a ) whether force is applied on M or m
( b ) the force applied on the system
(c ) Can’t be predicted.
( d ) None of these
Ans:- (a)
61. A body is moving with uniform velocity, then
( a ) no force must be acting on the body.
( b ) exactly two forces must be acting on the body
( c ) body is not acted upon by a single force.
( d ) the number of forces acting on the body must be even
Ans:- (c)
62. Who asserted that the natural state of body is the state of rest
( a ) Newton
( b ) Galileo
( c ) Einstein
( d ) Aristotle
Ans:- (d)
63. A body of mass 32 kg is suspended by a spring balance from the roof of a vertically operating lift and going downward from rest. At the instant the lift has covered 20 m and 50 m, the spring balance showed 30 kg and 36 kg respectively. Then the velocity of the lift is
( a ) decreasing at 20 m, and increasing at 50 m
( b ) increasing at 20m and decreasing at 50 m
( c ) continuously decreasing at a steady rate throughout the journey
( d ) constantly increasing at constant rate throughout the journey.
Ans:- (b)
64. A triangular block of mass M with angles 30°, 60°, and 90° rests with its 30°– 90° side on a horizontal table. A cubical block of mass m rests on the 60°– 30° side. The acceleration which M must have relative to the table to keep m stationary relative to the triangular block assuming frictionless contact is
( a ) g
( b ) g/√2
( c ) g/ √3
( d ) g/√5
Ans:- (c)
65. In an explosion, a body breaks up into two pieces of unequal masses. In this
( a ) both parts will have numerically equal momentum
( b ) lighter part will have more momentum
( c ) heavier part will have more momentum
( d ) both parts will have equal kinetic energy
Ans:- (a)
66. An object of mass 10 kg moves at a constant speed of 10 ms–1. A constant force, that acts for 4 sec on the object, gives it a speed of 2 ms–1 in opposite direction. The force acting on the object is
( a ) –3 N
( b ) –30 N
( c ) 3 N
( d ) 30 N
Ans:- (b)
67. Apparent weight of a body = actual weight of the body, if the body ………………………….
( a ) Moves with increasing velocity
( b ) Remains at rest
( c ) Remains in a state of uniform motion
( d ) Option (b) and (c)
Ans:- (d)
68. A toy gun consists of a spring and a rubber dart of mass 16 g. When compressed by 4 cm and released, it projects the dart to a height of 2 m. If compressed by 6 cm, the height achieved is
( a ) 3 m
( b ) 4 m
( c ) 4.5 m
( d ) 6 m
Ans:- (c)
69. Which is the type of inertia?
( a ) Inertia of rest
( b ) Inertia of motion
( c ) Inertia of direction
( d ) All the above options
Ans:- (d)
70. The mass of a body is 2 kg. It weight is
( a ) 19.6 N
( b ) 20 N
( c ) 30 N
( d ) 40 N
Ans:- (a)
71. Forces acting for a short duration are called ———–
( a ) Short force
( b ) Interval force
( c ) Impulsive forces
( d ) Interrupting force
Ans:- (c)
72. A car travelling at a speed of 30 km/h is brought to a halt in 4 m by applying brakes. If the same car is travelling at 60 km/h, it can be brought to halt with the same braking power in
( a ) 8 m
( b ) 16 m
( c ) 24 m
( d ) 32 m
Ans:- (b)