Mechanical Operations

1: In ball mill operation, the feed size (D_f in meters) and the ball diameter (D_b in metres) are related as ( where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hard ness))

A. `D_b^2 = K.D_f`

B. `D_b = K.D_f`

C. `D_b^3 = K.D_f`

D. `D_b^2 = K.D_f^2`

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A. Plastic chips are called non-cohesive solids

B. Kick's crushing law is, P/m = K . ln`((overline(D)_(sa))/(overline(D)_(sb)))`

C. Communition is a generic term for size enlargement operation

D. Energy required in kwh per ton of product, such that 80% of it passes through a 200 mesh screen, is called 'Work index'.

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A. `pi`

B. (`pi`/`6)^(1//3)`

C. (`pi`/`6)^(1//2)`

D. `pi`/3

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4: Velocity of a small particle of diameter 'D_p' at a distance 'r' from the rotational axis of a cyclone rotating at an angular speed `omega` is given by (the other symbols are as per standard notation)

A. `( D_p/18 . (Ps - p)/(mu)) omega ^2 r`

B. `( D_p^2/18 . (Ps - p)/(mu)) omega r^2`

C. `( D_p/18 . (Ps - p)/(mu)) omega ^2 r^2`

D. `( D_p^2/18 . (Ps - p)/(mu)) omega^2 r`

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5: The specific surface of spherical particles is given by (where D and`rho` are diameter and density of particle).

A. `(6)/(D.rho)`

B. `(2)/(D.rho)`

C. `(4)/(D.rho)`

D. `(12)/(D.rho)`

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