Mechanical Operations Multiple Choice Questions on “Open and Closed Circuit Grinding”.
1. As consolidation occurs, the rate _____
a) Increases
b) Decreases
c) Remains same
d) Has no change
Answer: b
Clarification: As consolidation occurs, the rate falls off because the resistance to the flow of liquid progressively increases.
2. The porosity of the particle is ______ at the bottom.
a) Greatest
b) Smallest
c) Broader
d) Same
Answer: b
Clarification: The porosity of the sediments is smallest at the bottom because of the compressive force due to the weight of particles.
3. Find the rate of sedimentation, if height of sludge and final height are 5.50 m and 2 m, assume the constant b to be 2?
a) 7
b) 5.5
c) 3.5
d) 2
Answer: a
Clarification: As rate is given by b (H-HF) = 2 (5.5-2) = 3*3.5 = 7 kg2m/s.
4. The shape of vessel has ___ effect on rate of sedimentation.
a) Devastating
b) Vast
c) Little
d) Most
Answer: c
Clarification: Provided that the walls of the vessel are vertical and cross sectional area does not vary with the depth, the shape has little effect on the rate.
5. The behavior of concentrated suspensions was analyzed by _____
a) Kynch
b) Newton
c) Einstein
d) Duckworth
Answer: a
Clarification: Behavior of concentrated suspensions during sedimentation was analyzed by Kynch, largely using considerations of continuity.
6. As the concentration approaches the limiting value, sedimentation velocity tends _______
a) Unity
b) Zero
c) Infinity
d) Finalized
Answer: b
Clarification: The sedimentation velocity tends to zero as the concentration approaches a limiting value corresponding to that of the sedimentation.
7. Kynch showed that the settling rate and concentration of that zone limits the capacity.
a) True
b) Fasle
Answer: a
Clarification: His method was based on the mathematical analysis of the batch settling, which showed that the settling rate and concentration of that zone limits the capacity.
8. What does the below equation represent?
a) Visual velocity
b) Final velocity
c) Upward velocity
d) Lower velocity
Answer: c
Clarification: The rate of upward propagation of such zone is constant and is the function of solids concentration i.e. C and v is the settling velocity.
9. What does the below equation represent?
a) Tangent to settling velocity
b) Angle of nip
c) Angle of settling
d) Sedimentation line
Answer: a
Clarification: The value of settling velocity VL is the slope of the tangent to the curve, this tangent intersects the vertical axis at Z=Z1.
10. If slope (m) = – tan Ө, therefore
a) VL = 0
b) VL = ZL
c) VL = – tan Ө
d) VL = – tan α
Answer: d
Clarification: We know that ZI – ZL = – Өi tan Ө, hence VL can be equal to – tan α.