Answer:
sorry if wrong
Explanation:
One sheave means that you are using a single drum winder. They are the worst! Double drum winders control easier, brake better and are much more efficient. They save time ( two skips or cages) and can be clutched to perform faster shift transport. A single drum is slow, unbalanced and can be a nightmare if it trips out during hoisting. If the brake system is not perfect it can be a real hairy experience. For a runaway single drum, there is no counterbalance effect. It always runs to destruction. With a double drum, the driver still has a chance to control the winder to a certain extent and he has two sets of brakes to rely on. A single sheave could also mean a shaft with a single compartment. No second means of escape unless there are ladders or stairways. Not a very healthy situation.
Those are just a few points. I am sure much more can be said in favor of a double drum winder and two or more sheaves in the headgear. Most of the shafts I have worked at have multiple winders and up to ten compartments. They all have a small single drum service winder for emergencies and moves of personnel during shift times. They are referred to as the Mary - Annes. Apparently, the name originated in the U.K. where an aristocratic mine owner named the first such winder after his mistress.
Answer:
Option B is correct
Explanation:
Let
Higher temperature =
Lower temperature = 
We know that COP is given by

We see that COP is depends only on the temperature difference & Temperature difference is maximum for the Carnot cycle.
Therefore the COP of reversible refrigeration cycle is always less then the COP of an irreversible refrigeration cycle when each operates between the same two thermal reservoirs.
Therefore option B is correct
Answer:
119.35 mm
Explanation:
Given:
Inside diameter, d = 100 mm
Tensile load, P = 400 kN
Stress = 120 MPa
let the outside diameter be 'D'
Now,
Stress is given as:
stress = Load × Area
also,
Area of hollow pipe =
or
Area of hollow pipe =
thus,
400 × 10³ N = 120 ×
or
D² = tex]\frac{400\times10^3+30\pi\times10^4}{30\pi}[/tex]
or
D = 119.35 mm
Answer:
The external pressure is p = -21.9 psf or p = -8.85 psf
Explanation:
Given :
Velocity of wind, v = 120 mi / hr
(wind direction factor)
= topographical factor (for flat terrain)
= velocity pressure at height h



But for height h = 30 ft,
= 0.98 (from table)

= 36.16
Now,
, so
(from table)

where, p = external pressure
G = 0.85 = gust factor (for typical rigid building)
(internal pressure co efficient)
Therefore putting the values,

p = -21.9 psf or p = -8.85 psf
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