# Mechanical Operations Questions and Answers – Open and Closed Circuit Grinding

This set of Mechanical Operations Multiple Choice Questions & Answers (MCQs) focuses on “Open and Closed Circuit Grinding”.

1. As consolidation occurs, the rate _____
a) Increases
b) Decreases
c) Remains same
d) Has no change

Explanation: 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
d) Same

Explanation: 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

Explanation: 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

Explanation: 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

Explanation: 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

Explanation: 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

Explanation: 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

Explanation: 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

Explanation: 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

Explanation: We know that ZI – ZL = – Өi tan Ө, hence VL can be equal to – tan α.

Sanfoundry Global Education & Learning Series – Mechanical Operations. 