Outline some of the major differences in the ways coal is mined
What will be an ideal response?
Coal near the surface is mined in what is often referred to as open pit or strip mines. In open pit mining, the
overburden (surface covering of earth) is removed and stored aside; the coal is removed; and the site is restored
using the overburden. Coal in deeper deposits is taken from underground mines. There are three main types of underground mines: shaft mines, slope mines, and drift mines. Shaft mines use vertical tunnels to gain access to
deeper coal deposits. Slope mines use tunnels that slope down more gently from the surface to the coal deposits.
Drift mines involve tunnels cut into the sides of mountains.
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Laying brick so that they touch the line is known as _____ .
A. laying brick correctly B. edging the line C. correcting the course D. crowding the line
Water, with a mass flux of 20 kg/min, at 50ºC and 2 MPa is mixed with steam at 2 MPa and 400ºC. If the quality at the exit is desired to be saturated liquid, the mass flux of the steam should be nearest:
A) 2 kg/min B) 4 kg/min C) 6 kg/min D) 10 kg/min
Weevil and billbug larvae do not have:
A) rasters B) mouthparts C) ?legs D) exoskeletons
The two internal chambers of a dual cell wide band oxygen sensor include ________ and ________
A) Air reference; diffusion B) Nernst; Pump C) Single; dual D) Inside; outside