Mechanical Operations problems
- 1. In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as ( where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hard ness))
Options- A. Db2 = K.Df
- B. Db = K.Df
- C. Db3 = K.Df
- D. Db2 = K.Df2 Discuss
Correct Answer: Db2 = K.Df
- 2. Grinding characteristic of a material is given by its
Options- A. HGI
- B. angle of repose
- C. shatter index
- D. abrasion index. Discuss
Correct Answer: HGI
- 3. A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 ?m/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is
Options- A. 0.90 ?m/s
- B. 1 ?m/s
- C. 22.1 ?m/s
- D. 0.02 ?m/s Discuss
Correct Answer: 1 ?m/s
- 4. In froth floatation, chemical agent added to cause air adherence is called
Options- A. collector
- B. frother
- C. modifier
- D. activator Discuss
Correct Answer: collector
- 5. Velocity of a small particle of diameter 'Dp' at a distance 'r' from the rotational axis of a cyclone rotating at an angular speed '?' is given by (the other symbols are as per standard notation)
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
- 6. __________ mills are termed as disintegrators.
Options- A. Cage
- B. Compartment
- C. Pebble
- D. All tumbling Discuss
Correct Answer: Cage
- 7. A cottrel precipitator makes use of the __________ for dusty air cleaning.
Options- A. electric spark
- B. corrona discharge
- C. alternating current
- D. none of these. Discuss
Correct Answer: corrona discharge
- 8. The sphericity of a solid particle of cubical shape is
Options- A. ?
- B. (?/6)1/3
- C. (?/6)1/2
- D. ?/3 Discuss
Correct Answer: (?/6)1/3
- 9. Compressibility co-efficient for an absolutely compressible cake is
Options- A. 0
- B. 1
- C. 0 to 1
- D. ? Discuss
Correct Answer: 1
- 10. In a roll crusher, the specific power consumption and the production rate is affected by the
Options- A. reduction ratio.
- B. differential roll speed.
- C. both (a) and (b).
- D. neither (a) nor (b). Discuss
Correct Answer: both (a) and (b).
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