50.

51.

52.

53.

54.

55.

Which of the following is true for a gating system in casting?
@ A gating system may be composed of a runner, riser, sprue, etc.
Gi) A gating system should have sudden or right-angled changes in direction
(ii) A gating system should fill the mold cavity completely before freezing
(^) Only (0) and (ii)
൯ All of the above (i), (ii) and (iii)
(C) Only (i) and (iii)
(D) None of the above (i), (ii) and (iii)

The energy required per unit mass to grind lime stone particle of very large size to 100 “mis
12.7 Kwh/ton. An estimate (using Bonds law) of the energy to grind the particles from a very
18786 5176 00 504८1115 :

(^) 6.35 Kwh/Ton (B) 9.0 Kwh/Ton

(C) 18.0 Kwh/Ton (D) 25.4 Kwh/Ton

What is the critical rotational speed in r.p.s. for a ball mill of 1.2 m diameter charged with
70 mm diameter balls?

(A) 0.5 (8) 1.0
(0 ೩76 (D) 0.66

For a sphere falling in a constant drag coefficient regime, its terminal velocity depends on its
diameter D as:

^ D ൫ 0
(0 2 (0) 1D

A 30% (by volume) suspension of spherical particles in a viscous oil has a hindered settling
velocity ‏ه‎ 4.4 (117/8. 17 the Richardson-zaki hindered settling index is 4.5, then the terminal

settling velocity of sand grain is:
(A) 0.9 wm (B) lum
(0 21.9 ‏سم‎ (D) 0.02 ‏سم‎

Separation factor of a cyclone separator having 0.5 m diameter and tangential velocity of
20 m/s is:

(A) 40 (B) 80
(C) 160 (D) 240

121/2022 12 A