Mechanical Operations problems
- 1. The sphericity of a cylinder of 1 mm diameter and length 3 mm is
Options- A. 0.9
- B. 0.78
- C. 0.6
- D. 0.5 Discuss
Correct Answer: 0.9
- 2. Size reduction mechanism used in Jaw crushers is
Options- A. attrition
- B. compression
- C. cutting
- D. impact Discuss
Correct Answer: compression
- 3. Pick out the wrong statement.
Options- A. Gape is the greatest distance between the crushing surfaces or the jaws.
- B. The angle of nip (2?) is the angle between roll faces at the level where they will j ust take hold of a particle and draw it in the crushing zone.
- C. Crushing efficiency is the ratio of the energy absorbed by the solid to the surfaces energy created by crushing.
- D. Reduction ratio is the ratio of the maximum size of the particles in the feed to that in the product. Discuss
Correct Answer: Crushing efficiency is the ratio of the energy absorbed by the solid to the surfaces energy created by crushing.
- 4. A widely used size reduction equipment for __________ is Bradford breaker.
Options- A. talc
- B. coal
- C. iron core
- D. wheat Discuss
Correct Answer: coal
- 5. The most suitable equipment used to devulcanise rubber scrap and to make water dispersion & rubber solution is a
Options- A. boundary mixer.
- B. propeller agitator.
- C. sharpies centrifuge.
- D. none of these. Discuss
Correct Answer: boundary mixer.
- 6. What is the selectivity index, if the grade of tailings & concentrate is the same?
Options- A. 0
- B. ?
- C. 1
- D. 0.5 Discuss
Correct Answer: 1
- 7. According to Taggart's rule for selecting between a gyratory crusher and a jaw crusher; the later should be used, if the hourly tonnage to be crushed divided by the square of the gape expressed in cm is less than
Options- A. 0.00184
- B. 0.0184
- C. 0.184
- D. 1.84 Discuss
Correct Answer: 0.0184
- 8. The constants (Kb, Kr and Kk) used in the laws of crushing (i.e., Bond's law, Rittinger's law and Kick's law) depend upon the
Options- A. feed material.
- B. type of crushing machine.
- C. both (a) & (b).
- D. neither (a) nor (b). Discuss
Correct Answer: both (a) & (b).
- 9. __________ conveyor is the most suitable for long distance transportation of cold, non-abrasive granular/irregular shape/fine materials.
Options- A. Bucket
- B. Belt
- C. Screw
- D. Apron Discuss
Correct Answer: Belt
- 10. A suspension of glass beads in ethylene glycol has a hindered settling velocity of 1.7 mm/s, while the terminal settling velocity of a single glass bead in ethylene glycol is 17 mm/s. If the Richardson-Zaki hindered settling index is 4.5, the volume fraction of solids in the suspension is
Options- A. 0.1
- B. 0.4
- C. 0.6
- D. none of these Discuss
Correct Answer: 0.6
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