**Points :**mechanics - mcqs, mechanics fill in the blanks, mechanics objective type questions 1. Plankâ€™s constant has the dimensions of

(a) energy

(b) work

(c) linear momentum

(d)

**angular momentum**

2. The unit of power is

(a)

**kilowatt**

(b) kilowatt-hour

(c) dyne

(d) joule

3. In the S.I. system, the unit of temperature is

(a)

**degrees centigrade**

(b) kelvin

(c) degrees celsius

(d) degrees fahrenheit

4. A cube has numerically equal volume and surface area. The volume of such a cube is

(a)

**216 units**

(b) 1000 units

(c) 2000 units

(d) 3000 units

5. In the S.!. system, the unit of energy is

(a) erg

(b)

**calorie**

(c) joule

(d) electron volt

6. ln the SI. system, the unit of force is

(a) watt

(b) dyne

(c)

**newton**

(d) poundal

7. Theunit of energy is

(a) 1/s

(b)

**watt-day**

(c) kilowatt

(d) gcm/s

^{2}

8. Of the following observed readings, which one is the most precise?

(a) 4567 gm

(b) 456.7 gm

(c) 45.67 gm

(d)

**4.567 gm**

9. If the volume of a cube is 1.76cm

^{3}, then the volume of twenty five such cubes is

(a) 4.4 x 10 cm

^{3}

(b) 44 cm

^{3}

(c)

**44.0 cm**

^{3}(d) 4400 cm

^{3}

10. The dimensions of power are

(a)

**ML**

^{2}/T^{3}(b) M

^{2}L/T

^{2}

(c) ML

^{2}/T

(d) ML/T

^{2}

^{2}

11. The dimensions of a couple are

(a)

**MLT**

^{2}(b) ML

^{2}

(c) MLT

^{-1}

(d) ML

^{-3}T

^{-2}

12. MLT

^{4}are the dimensions of

(a) power

(b)

**momentum**

(c) force

(d) couple

13. The density of wood is 0.5 gm per c.c. in the C.CS. system of units. The corresponding value in the M.K.S. system is

(a)

**500**

(b) 5

(c) 0.5

(d) 5000

14. If the error in the measurement of the radius of a sphere is 1%, then the error in the measurement its volume is

(a) 1%

(b)

**3%**

(c) 5%

(d) 8%

15. The dimensional formula for torque is

(a)

**ML**

^{2}T^{2}(b) MLT

^{2}

(c) MLT

^{3}

(d) none of these

16. The surface tension of a liquid is 70 dynes/cm; it may be expressed in the M.K.S. system as

(a) 70 newtons/m

(b)

**7x10**

^{2}newton/m(c) 7x10

^{2}newton/m

^{2}

(d) 7x10

^{3}newton/m

17. One nanometer is equal to

(a) 10 mm

(b) 10

^{-6}cm

(c) 10

^{-7}cm

(d)

**10**

^{-9}cm18. Which one of the following is not a unit of time?

(a) Lunar month

(b) Leap year

(c) Parallactic second

(d)

**Solar day**

19. The distance traversed by the particle in four seconds is

(a) 60m

(b)

**55m**

(c) 25m

(d) 30m

20. The numerical ratio of displacement to distance is

(a) always less than one

(b) always equal to one

(c) always more than one

(d)

**equal to or less than one**

21. A body sliding on a smooth inclined plane requires 4 seconds to reach the bottom, starting from rest at the top. how much time does it take to cover one fourth the distance starting from rest at the top?

(a) 1 second

(b)

**2 seconds**

(c) 4 seconds

(d) 16 seconds

22. If a ball X, is dropped gently from a tower and at exactly the same moment, another ball Y, is fired horizontally.

(a)

**X and Y reach the ground simultaneously**

(b) X reaches earlier

(c) Y reaches earlier

(d) X and Y do not reach the ground at all

23. Joule X Sec. is the unit of

(a) energy

(b) momentum

(c)

**angular momentum**

(d) power

24. If a ball is just allowed to fall from the window of a moving train, the ball will hit the ground, following a

(a) straight line path

(b)

**parabolic path**

(c) hyperbolic path

(d) circular path

25. A stone released with zero velocity from the top of a tower reaches the ground in 4 sec. The height of the tower is about

(a) 20m

(b)

**78.4m**

(c) 40m

(d) 160m

26. A body goes from A to B at a speed of 60 km/hr and comes back from B to A at a speed of 50km/hr. What s the average velocity?

(a) 55 km/hr

(b) 54.5 km/hr

(c) 54km/hr

(d)

**zero**

27. A person takes an aim at a monkey sitting on a tree and fires a bullet. Seeing the smoke, the monkey begins to fall freely. The bullet will

(a)

**hit the monkey**

(b) go above the monkey

(c) go below the monkey

(d) hit or miss the monkey depending upon the velocity of the bullet

28. If a body covers 200 cms in the first 2 seconds and 220 cms in the next 4 seconds, the velocity of the body at the end of the 7th second is

(a) 15cm/s

(b) 115cm/s

(c) 20cm/s

(d)

**none of these**

29. In the previous question, the total height of fall is

(a) 50m

(b)

**57m**

(c) 78.4m

(d) 19.6m

30. A body is released from a great height and falls freely towards the earth. Another body is released from the same height exactly one second later. The separation between the two bodies, 2 seconds after the release of the second body is

(a) 4.9m

(b) 9.8m

(c) 14.6 m

(d)

**245 m**

31. A particle moves in a plane with a constant acceleration in a direction different from the initial velocity. The path of the particle is

(a) a straight line

(b) an are of a circle

(c)

**a parabola**

(d) an ellipse

32. A juggler is throwing bails vertically upwards in air at intervals of is. He throw another bail when the previous bail is at its highest point. The maximum height to which each ball rises is

(a) 14.7m

(b) 9.8m

(c)

**4.9m**

(d) 2.45m

33. Which of the following quantities is scalar?

(a) Electric field

(b) Velocity

(c) Angular momentum

(d)

**Electrostatic potential.**

34. The range of a particle when launched at an angle of 15Â° with the horizontal is 1.5 km. What is the range of the projectile when launched at an angle of 45Â° to the horizontal?

(a) 1.5 km

(b)

**3.0km**

(c) 6.0 km

(d) 0.75 km

35. The minimum number of unequal forces whose vector sum can be equal to zero, is

(a) 4

(b) 2

(c)

**3**

(d) 1

36. Two parallel forces not having the same line of action form a couple if they are

(a) like and equal

(b) like and unequal

(c) unequal and unlike

(d)

**equal and unlike**

37. When the following three forces of 5 N, 10 N and 20 N act on a body, then the body is

(a) at rest

(b) moving with a uniform velocity

(c) in equilibrium

(d)

**moving with an acceleration**

38. When a body is stationary

(a) there is no force acting on it

(b) the forces acting on it are not in contact with it

(c)

**the combination of forces acting on It balance each other**

(d) the body is in vacuum

39. Identify the scalar quantity.

(a) Force

(b) Acceleration

(c) Displacement

(d)

**Work**

40. Newtonâ€™s three laws of motion are, the first, the second and third laws. We can derive

(a) the second and third laws from the first law

(b)

**the third and first laws from the second law**

(c) the first and second laws from the third law

(d) All the laws are independent of each other

41. A Diwali rocket is ejecting 0.05 kg of gases per second at a velocity of 400 m/s. The accelerating force on the rocket is

(a) 20 dynes

(b)

**20 newtons**

(c) 22 kg

(d) 4000 newtons

42. In the above problem, if the lift ascends with a constant velocity of 2m/s, the reading on the balance will be

(a)

**2 kg wt**

(b) 4 kg. wt

(c) zero

(d) 1 kg. wt

43. Conservation of linear momentum is equivalent to

(a) Newtonâ€™s 1st law of motion

(b)

**Newtonâ€™s 2nd law of motion**

(c) Newtonâ€™s 3rd law of motion

(d) none of above

44. In an elastic collision between two particles the quantities conserved are

(a) the speed of each particle

(b) the linear momentum of each particle

(c) the kinetic energy of each particle

(d)

**their total kinetic energy**

45. A particle at rest suddenly disintegrates into two particles of equal masses which start moving. The two fragments will

(a) move in the same direction with equal velocities

(b) move in any two directions with any velocity

(c)

**move in opposite directions with equal speeds**

(d) move in opposite directions with unequal velocities

46. When two bodies collide elastically then

(a) kinetic energy of the system alone is conserved

(b) only momentum is conserved

(c)

**both energy and momentum are conserved**

(d) neither energy nor momentum is conserved

47. A bullet hits and gets embedded in a solid block resting on a horizontal frictionless table. What is conserved?

(a) Momentum and Kinetic Energy

(b) Kinetic Energy alone

(c)

**Momentum alone**

(d) Neither Momentum nor Kinetic Energy

48. A light and a heavy body have equal kinetic energies. Which one has a greater momentum?

(d) The light body

(b)

**The heavy body**

(c) Both have equal momentum

(d) It is not possible to say anything without additional information

49. If a trader sells his article, weighing equal quantities from the two pans of a balance having unequal arms, he

(a) loses

(h) gains

(c) neither loses nor gains

(d)

**nothing can be said with certainty**

50. If the tension in the cable of a 1000 kg elevator is 1000 kg weight, the elevator

(a) is accelerating upwards

(b) is accelerating downwards

(c) may be at rest or accelerating

(d)

**may be at rest or in uniform motion**

51. Consider an elevator moving downwards with an acceleration a, the force exerted by a passenger of a mass m on the floor of the elevator is

(a) ma

(b) ma-mg

(c)

**mg-ma**

(d) mg+ma.

52. A cyclist turns around a curve at 15 miles/hr. If he turns at double the speed, the tendency to overturn is

(a) doubled

(b)

**quadrupled**

(c) halved

(d) unchanged

53. A man in a lift will weigh more when

(a)

**the lift begins to go up**

(b) the lift is going up straight

(c) the lift is slowing down while ascending

(d) the lift is descending freely

54. Two forces, each of magnitude F have a resultant of the same magnitude F. The angle between the two forces is

(a) 45Â°

(b

**120Â°**

(c) 150

(d) 60Â°

55. If a particle moves in a circle, describing equal angles in equal times, its velocity vector

(a) remains constant

(b) changes in magnitude

(c)

**changes in direction**

(d) changes both in magnitude and direction

56. A particle is moving in a circle with uniform speed. It has constant

(a) velocity

(b) acceleration

(c)

**kinetic energy**

(d) displacement

57. A body is moving in a circular path with a constant speed. It has

(a) a constant velocity

(b) a constant acceleration

(c)

**an acceleration of constant magnitude**

(d) an acceleration which varies with time

58. An aeroplane is taking a turn in a horizontal plane. While so turning,

(a) it remains horizontal

(b)

**it inclines inwards**

(c) it inclines outwards

(d) its wings become vertical

59. A particle revolves round a circular path with a uniform speed. The centripetal acceleration of the

particle is

(a) along the circumference of the circle

(b) along the tangent

(c)

**along the radius**

(d) zero

60. A cyclist taking a turn bends inwards while a car passenger taking the same turn is thrown outwards. The reason is

(a) the car is heavier than the cycle

(b) the car has four wheels, while cycle has two

(c)

**the cyclist has to counteract the centrifugal force, while the passenger is only thrown by it**

(d) the difference in the speed of the two

61. When a body moves with a constant speed in a circle in a horizontal plane, then, there is no

(a)

**work done on it**

(b) force acting on it

(c) acceleration in it

(d) change in its velocity

62. A body at rest may have

(a) speed

(b) velocity

(c) momentum

(d)

**energy**

63. A can filled with water is revolved in a vertical circle of radius 4m but the water Just does not fall down. The time period of a revolution will be

(a) 1 sec

(b) 10 sec

(c) 8sec

(d)

**4sec**

64. When a mass is rotating in a plane about a fixed point, its angular momentum is directed along

(a) the radius

(b) the tangent to the orbit

(c)

**a line perpendicular to the plane of rotation**

(d) none of these

65. A car sometimes overturns while taking a turn. When it overturns, it is

(a)

**the inner wheel which leaves the ground first**

(b) the outer wheel which leaves the ground first

(c) both the wheels which leave the ground simultaneously

(d) either wheel which leaves the ground first

66. In the above question the centre of mass

(a) moves in the direction of larger mass.

(b) moves in the direction of smaller mass.

(c)

**remains unchanged**

(d) may move in any direction depending upon the spring constant.

67. When a torque acting upon the system is zero, which of the following will be coustant.

(a) force

(b) linear momentum

(c)

**anguIar momentum**

(d) linear impulse

68. Angular momentum of a body is defined as the product of

(a) mass and angular velocity

(b) centripetal force and radius

(c) linear velocity and angular velocity

(d)

**moment of inertia and angular velocity**

69. Conversion of heat into electrical energy can be achieved by using a

(a) hydrometer

(b)

**thermocouple**

(c) voltmeter

(d) photo-electric tube

70. Work is always done on a body when

(a) a force acts on it

(b) it moves through a certain distance

(c)

**it experiences an increase in energy through a mechanical influence**

(d) none of the three

71. The rotational analogue of force in linear motion is

(a)

**torque**

(b) weight

(c) moment of inertia

(d) angular momentum

72. A lead ball falling freely from a height strikes the ground. As a result its temperature rises. This is due to

(a) friction due to air

(b) conversion of mass into heat

(c) conversion of chemical energy into heat

(d)

**conversion of mechanical energy into heat**

73. If a shell fired from a canon explodes in mid-air

(a) its total momentum increases

(b) its total momentum decreases

(c)

**its total kinetic energy increases**

(d) its total kinetic energy decreases

74. A wound watch spring

(a) has no energy stored in it

(b) has kinetic energy stored in it

(c)

**has mechanical potential energy stored in it**

(d) has electrical energy stored in it

75. If a 5 kg body falls to the ground from a height of 30 m and if all its mechanical energy is converted into heat, the heat produced will be

(a)

**350 cal**

(b) 150 cal

(c) 60 cal

(d) 6 cal

76. The efficiency of a simple machine is given by

(a)

**mechanical advantage/velocity ratio**

(b) mechanical advantage x velocity ratio

(c) velocity ratio + mechanical advantage

(d) input=output

77. A pump motor is used to deliver water at a certain rate from a given pipe. To obtain twice as much water from the same pipe in the same time, the power of the motor has to be increased to

(a) 2 times

(b) 4 times

(c)

**8 times**

(d) 16 times

78. When a torque acting upon a system is zero, which of the following will be constant?

(a) Force

(b) Linear momentum

(c)

**Angular momentum**

(d) Linear impulse

79. It is easier to draw up a wooden block along an inclined plane than to haul it up vertically, principally, because

(a) the friction is reduced

(b) the mass becomes smaller

(c)

**only a part of the weight has to be overcome**

(d) g becomes smaller

80. The rotational analogue of mass in linear motion is

(a) torque

(b) weigh

(c)

**moment of inertia**

(d) angular momentum

81. When a mass is rotating in a plane about a fixed axis, its angular momentum is directed along

(a) the radius

(b) the tangent to the orbit

(c) the line at an angle of 50 to the plane of rotation

(d)

**the axis of rotation**

82. An air bubble and a steel ball in water

(a) attract each other

(b)

**repel each other**

(c) neither attract nor repel each other

(d) may attract or repel depending upon sizes

83. The moment of momentum is called

(a) couple

(b) torque

(c) impulse

(d)

**angular momentum**

84. A man sitting on a rotating table with his arms stretched outwards. If he suddenly folds his arms inside,

(a) his angular velocity will decrease

(b) his angular velocity remains constant

(c)

**his moment of inertia decreases**

(d) his angular momentum increases

85. If the distance between two masses is doubled, the gravitational attraction between them

(a) is doubled

(b) becomes four times

(c) is reduced to half

(d)

**is reduced to a quarter**

86. The length of a secondâ€™s pendulum on earth is about

(a) 80m

(b)

**100cm**

(c) 120 cm

(d) 160 cm

87. A particle is moving in a circle with uniform speed. Its motion is

(a) periodic and simple harmonic

(b)

**periodic but not simple harmonic**

(c) a periodic

(d) none of the above

88. When a body is immersed in a liquid it loses

(a) mass

(b)

**weight**

(c) both mass and weight

(d) neither mass nor weight

89. When a body of mass m is taken to the bottom of a deep mine, its

(a) mass increases

(b) mass decreases

(c) weight increase

(d)

**weight decreases**

90. The orbital speed of Jupiter is

(a) greater than the orbital speed of earth

(b)

**less than the orbital speed of earth**

(c) equal to the orbital speed of earth

(d) zero

91. With the rise of temperature, the surface tension of liquids

(a)

**decreases**

(b) increases

(c) remains unchanged

(d) first increases, then decreases

92. Which is the most intense planet of the solar system?

(a) Saturn

(b) Mars

(c)

**Venus**

(d) Mercury

93. A geostationary satellite

(a)

**revolves about the polar axis**

(b) has a time period less than that of a near earth satellite

(c) moves laster than the near earth satellite

(d) is stationary in space

94. The most characteristic property of a liquid is

(a) elasticity

(b) formlessness

(c) fluidity

(d)

**volume conservation**

95. With the rise of temperature, the angle of contact of a liquid

(a)

**increases**

(b) decreases

(c) becomes zero

(d) first increases, then decreases

96. The end of a glass tube becomes spherical on heating due to

(a)

**surface tension**

(b) viscosity

(c) gravity

(d) friction

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