# Mechanical Operations Questions and Answers – Size Reduction

This set of Mechanical Operations Multiple Choice Questions & Answers (MCQs) focuses on “Size Reduction”.

1. According to Rittingers law, work required is proportional to _________
a) Energy Consumed
b) Surface area created
c) Final Volume
d) Initial feed

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

2. 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

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

3. What does the below equation represent?

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

4. 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

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.
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5. On which of the given, Kick’s law is based?
a) Cumulative analysis
b) Frequency analysis
c) Stress analysis
d) Screen analysis

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

6. According to Kick, the work required for crushing a mass of material is ____
a) Zero
b) Constant
c) Unity
d) Infinite

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

7. 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

Explanation: The reduction ratio for a crusher is defined as the ratio of feed opening to the discharge opening i.e. Dsa/Dab.

8. What does the below equation represent? a) Arrhenius Law
b) Kick’s Law
c) Bond Law
d) Rittingers Law

Explanation: The formula above represents the Kick’s law, where P is the power required, m is the mass and Dsa/Dab is the reduction ratio and Kk is the kick’s constant.

9. Kick’s law holds well for ____
a) Fine crushing
b) Simple crushing
c) Full crushing
d) Coarse crushing

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

10. The below equation is in the form of____ a) Experimental relation
b) Empirical relation
c) Generalized relation
d) Actual relation

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.

Sanfoundry Global Education & Learning Series – Mechanical Operations.

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