Q. For a laminar flow of a liquid metal over a flat plate, the thicknesses of the velocity and thermal boundary layers are 𝛿𝑣 and 𝛿𝑡 respectively. Kinematic viscosity (viscosity/density) of liquid metal is significantly lower than its thermal diffusivity [thermal conductivity / (density × specific heat)]. Based on this information, pick the correct option. […]
Q. Sum of the series 5, 10, 15,…………………… , 500 is Sol:
Sum of the series 5, 10, 15,……., 500 is Read More »
Q. A 20 m long steel tape used for survey is found to be short by 10 cm. If the area measured with the steel tape is 5000 m2, the actual area in m2 is . Ans: 4945.0-4955.0
A 20 m long steel tape used for survey is found to be short by 10 cm Read More »
Q. In a level terrain, a vertical orebody of 20 m uniform width is worked by surface mining method. The density of the ore is 2.5 tonne/m3. The ultimate pit has a depth of 60 m, width of 20 m at pit bottom, and a pit slope of 45o. The overall stripping ratio for this
In a level terrain, a vertical orebody of 20 m uniform width is worked by surface mining Read More »
Q. The immediate roof of a mine is supported by bolts of length 1.5 m, arranged in 1.2 m x 1.2 m grid pattern. If the unit weight of roof rock is 2.25 tonne/m3 and load carrying capacity of each bolt is 7.5 tonne, the factor of safety of the support system is . Ans:
The immediate roof of a mine is supported by bolts of length 1.5 m, arranged in 1.2 m Read More »
Q. In underground face blasting, the pull is found to be 10% less than the drillhole length. The headings of 3.6 m width are supported by prop density of 1.44/m2. The hole length is 1.5 m, and 6 rounds of blasting are done in the panel per shift. The number of props to be erected
In underground face blasting, the pull is found to be 10% less Read More »
Q. The experiment to determine permeability of a soil sample is illustrated below. The cross- sectional area of the sample is 20.0 cm2. The permeability of the soil sample in cm/s is Ans: 0.02-0.02
The experiment to determine permeability of a soil sample is illustrated below Read More »
Q. An SDL of 1.0 tonne capacity operates with a cycle time of 6 minutes. The dimension of the face is 4 m x 3 m. Five blasts are conducted per shift with an average pull of 1.2 m. If the density of blasted coal is 0.8 tonne/m3, the time required by the SDL in
An SDL of 1.0 tonne capacity operates with a cycle time of 6 minutes Read More »
Q. In a direct rope haulage operating along a 1500 m long incline, 180 tonne of coal is hauled in 7 hours. The average rope speed is 7.5 km/h. The set changing time for the tubs is 2 minutes each at the top and bottom of the incline. If the tub capacity is 1.0 tonne,
In a direct rope haulage operating along a 1500 m long incline Read More »
Q. Air enters a bord and pillar panel at 10 ppm CO and 20.78% O2. The air at the panel return has 80 ppm CO and 20.52% O2. The ‘Graham’s ratio’ for the status of fire in the panel in % is Ans: 2.65-2.75
Air enters a bord and pillar panel at 10 ppm CO and 20.78% O2 Read More »
