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51
For the same roadway roughness, area, length and velocity condition the ratio of resistances of a square roadway to that of a rectangular roadway having width and height ratio. 2 : 1 is
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Answer: Option B
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52
The mean velocity of air current through an airway of 9m2 cross-sectional area is found to be 1.5 m/s, If the mean methane content of air current is 0.6%, the layering index will be
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Answer: Option A
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53
Air at dry bulb temperature of 27°C enters a 1200 m deep shaft. The specific heat of air-water vapour mixture is 1.03 KJ/kg °C. If the air goes through constant-moisture adiabatic auto compression, the air temperature at the bottom of the shaft in °C is
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Answer: Option D
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54
The blade tip speed of a backward bladed centrifugal fan running at 300 rpm delivers 120 m3/s of air. If the tip speed of the blade is 47.12 m/s and width of the fan is 1.3 m then the radial velocity of air at the periphery of the impeller in m/s is
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Answer: Option A
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55
An underground coal mine panel produces 520 tonnes per day deploying 220, 200 and 192 persons in three shifts. As per CMR 1957, the minimum quantity of air in m3/min to be delivered at the last ventilation connection of the panel is
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Answer: Option B
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56
The formula for finding the velocity of air . . . . . . . .
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Answer: Option A
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57
Match the following:
Mine gas Principal constituent
P. Stink damp 1. CO
Q. White damp 2. H2S
R. Black damp 3. CH4
S. Fire damp 4. CO2
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Answer: Option C
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58
The lower and upper limit of methane - air explosive mixture is
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Answer: Option B
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59
The sp.gr of CO2
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Answer: Option B
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60
In a mine between upcast shaft and downcast shaft, two airways are connected in parallel and their resistances are 100 and 120 Ns-2m-8 respectively. The resistance of upcast shaft, downcast shaft and the fan drifts are 10, 20, and 5 Ns-2m-8 respectively. The rate of airflow through the split airway having resistance of 100 Ns-2m-8 in m3/s is
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Answer: Option E
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