Mechanical Operations

81. Critical speed of rotation, N (in rps - rotation per second) of a trammel is equal to (where, g = acceleration due to gravity = 9.81 m/sec2 and, r = radius of trammel, metre.)

1. (1/2π). √(g/r)
2. (1/π). √(g/r)
3. ½ √(g/r)
4. 2π. √(g/r)

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82. Crushing efficiency is the ratio of the

1. Surface energy created by crushing to the energy absorbed by the solid
2. Energy absorbed by the solid to that fed to the machine
3. Energy fed to the machine to the surface energy created by crushing
4. Energy absorbed by the solid to the surface energy created by crushing

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83. Crushing efficiency of a machine ranges between _________ percent.

1. 0.1 to 2
2. 5 to 10
3. 20 to 25
4. 50 to 70

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84. Crushing of mineral particles is accomplished in a 'cage mill', when one or more alloy steel bars are revolved in opposite directions. It is a type of _________ mill.

1. Impact
2. Roll
3. Vibratory
4. None of these

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85. Cumulative analysis for determining surface is more precise than differential analysis, because of the

1. Assumption that all particles in a single fraction are equal in size
2. Fact that screening is more effective
3. Assumption that all particles in a single fraction are equal in size, is not needed
4. None of these

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86. Cyclones are used primarily for separating

1. Solids
2. Solids from fluids
3. Liquids
4. Solids from solids

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87. Diatomaceous earth is a/an

1. Explosive
2. Filter aid
3. Filter medium
4. Catalyst

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88. Dispersion of a gas through liquid is done by using a

1. Sparger
2. Kneader
3. Masticator
4. None of these

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89. Dry powdery solid materials are transported by a _________ conveyor.

1. Belt
2. Bucket
3. Screw
4. None of these

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90. During agitation of liquids, power consumption during laminar flow is not proportional to the

1. Density of the liquid
2. Viscosity of the liquid
3. Cube of impeller diameters
4. Square of rotational speed

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