Mechanical Operations problems
- 1. Work index is the gross energy (kWh/tonne of feed) necessary to reduce a very large feed to such a size that 80% of product particles will pass through a 0.1 mm screen. The value of work index determined for wet grinding should be multiplied with __________ to get the same for dry grinding.
Options- A. 1.0
- B. 0.5
- C. 1.34
- D. 4.34 Discuss
Correct Answer: 1.34
- 2. __________ are mixed using ribbon blenders.
Options- A. Lumpy solids and low viscosity liquids
- B. Dry powders
- C. High viscosity liquids
- D. Thick pastes Discuss
Correct Answer: Dry powders
- 3. The critical speed of a trommel (N) is related to its dia (D) as
Options- A. N ?
- B. N ? D
- C. N ? D
- D. N ?
Discuss
Correct Answer: N ?
- 4. The process by which fine solids is removed from liquids is termed as
Options- A. decantation
- B. flocculation
- C. sedimentation
- D. classification Discuss
Correct Answer: sedimentation
- 5. For crushing of solids, the Rittinger's law states that the work required for crushing is proportional to
Options- A. the new surface created.
- B. the size reduction ratio.
- C. the change in volume due to crushing.
- D. none of these. Discuss
Correct Answer: the new surface created.
- 6. Activators are those chemicals which help buoying up one mineral in preference to the other in the froth floatation process. Which of the following is an activator?
Options- A. Cresylic acid
- B. Copper sulphate
- C. Calcium carbonate
- D. Sodium carbonate Discuss
Correct Answer: Copper sulphate
- 7. Which of the following achieves the least reduction ratio for a given feed size?
Options- A. Jaw crusher
- B. Roll crusher
- C. Cone crusher
- D. Gyratory crusher Discuss
Correct Answer: Roll crusher
- 8. As per Taggart's formula, the capacity (kg/hr) of Jaw & Gyratory crushers (for gapes of 10 to 60 cms) is equal to (where, L = Length of feed opening, cms S = Maximum width of discharge opening, cms )
Options- A. LS
- B. 93 LS
- C. 250 LS
- D. LS Discuss
Correct Answer: 93 LS
- 9. Which of the following crushing laws is most accurately applicable to the fine grinding of materials?
Options- A. Bond's crushing law
- B. Kick's law
- C. Rittinger's law
- D. None of these. Discuss
Correct Answer: Rittinger's law
- 10. For coarse reduction of hard solids, use
Options- A. impact
- B. attrition
- C. compression
- D. cutting Discuss
Correct Answer: compression
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