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# Mechanical Operations MCQ’s – Size Reduction

According to Rittingers law, work required is proportional to _________

a) Energy Consumed

b) Surface area created

c) Final Volume

d) Initial feed

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Answer: b

Explanation: The Rittingers law states that “The work required in crushing is directly proportional to the new surface area created”.

Following Rittingers law, Crushing efficiency is ____

a) Independent of feed material

b) Independent of size of feed and product

c) Independent of energy consumed

d) Independent of area

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Answer: b

Explanation: Crushing efficiency is constant and for a given machine and feed material, is independent of size of feed and product.

What does the below equation represent?

a) Arrhenius Law

b) Kick’s Law

c) Bond Law

d) Rittingers Law

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Answer: d

Explanation: The formula above represents the Rittingers law, where P is the power required, m is the mass and Kf is the constant.

Rittingers law is applicable only when _____

a) New particles are created

b) New surface area is created

c) Energy is created

d) Energy is absorbed

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Answer: b

Explanation: Rittingers law applies well where new surface area is created and hold good for fine grinding where increase is surface area per unit mass is large.

On which of the given, Kick’s law is based?

a) Cumulative analysis

b) Frequency analysis

c) Stress analysis

d) Screen analysis

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Answer: c

Explanation: Kick proposed another law, based on the stress analysis of plastic deformation within the elastic limits.

According to Kick, the work required for crushing a mass of material is ____

a) Zero

b) Constant

c) Unity

d) Infinite

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Answer: b

Explanation: The kick’s law states that the work required for crushing a mass of material is constant for the same reduction ratio.

The ratio of initial particle size to final particle size is defined as _____

a) Reduction ratio

b) Kick’s ratio

c) Rittingers ratio

d) Bond’s ratio

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Answer: b

Explanation: The reduction ratio for a crusher is defined as the ratio of feed opening to the discharge opening i.e. D_{sa}/D_{ab}.

What does the below equation represent?

a) Arrhenius Law

b) Kick’s Law

c) Bond Law

d) Rittingers Law

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Answer: b

Explanation: The formula above represents the Kick’s law, where P is the power required, m is the mass and D_{sa}/D_{ab} is the reduction ratio and Kk is the kick’s constant.

Kick’s law holds well for ____

a) Fine crushing

b) Simple crushing

c) Full crushing

d) Coarse crushing

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Answer: d

Explanation: Kick’s law holds good for coarse crushing and amount of surface produced is less.

The below equation is in the form of____

a) Experimental relation

b) Empirical relation

c) Generalized relation

d) Actual relation

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Answer: c

Explanation: The generalized relation is in the form of the above equation that is the form of the differential equation, where the value of ‘n’ varies.