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lorasvet [3.4K]
3 years ago
11

Many households in developing countries prepare food over indoor cook stoves with no ducting system to exhaust the combustion pr

oducts outside. A woman in a household lights a fire in her cookstove at 4 pm. The fire emits benzo(a)pyrene, a carcinogenic compound, at a rate of 0.01 ng/min. The house has a size of 40 m3 and a ventilation rate of 1 m3/h. The ambient indoor air concentration of benzo(a)pyrene was 0.2 ng/m3 when she started the fire, but no significant concentration of benzo(a)pyrene is found in the outdoor air. What is the indoor benzo(a)pyrene concentration in the household at 6 pm?
Engineering
1 answer:
lorasvet [3.4K]3 years ago
7 0

Answer:

   C = 0.22857 ng / m³

Explanation:

Let's solve this problem for part the total time in the kitchen is

          t = 2h (60 min / 1h) = 120 min

The concentration (C) quantity of benzol pyrene is the initial quantity plus the quantity generated per area minus the quantity eliminated by the air flow. The amount removed can be calculated assuming that an amount of extra air that must be filled with the pollutant

amount generated

         C = co + time_generation rate / (area_house + area_flow)

         C = 0.2 + 0.01 120 / (40+ 2)

         C = 0.22857 ng / m³

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Serviceable wheel bearings can be repacked by removing the dust cap and the cotter pin must be replaced with a new one every time it is removed. Therefore, both Tech A and B are correct.

Sealed bearing assemblies are typically prefilled with lubricant. They also make a more reliable and consistent installation process due to the fact that every into comes preset at the proper clearance.

Furthermore, the serviceable wheel bearings can be repacked by removing the dust cap, filling it with grease, and reinstalling it. Also, cotter pin must be replaced with a new one every time it is removed.

Therefore, both tech A and B are correct.

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2 years ago
What do Engineering Systems achieve?
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Answer:

Systems Engineering helps avoid omissions and invalid assumptions, helps to manage real world changing issues, and produce the most efficient, economic and robust solution.

Explanation:

3 0
3 years ago
Calculate the time taken to completely empty aswimming pool 15
user100 [1]

Answer:

Time needed to empty the pool is 401.35 seconds.

Explanation:

The exit velocity of the water from the orifice is obtained from the Torricelli's law as

V_{exit}=\sqrt{2gh}

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'h' is the head under which the flow of water occurs

Thus the theoretical discharge through the orifice equals

Q_{th}=A_{orifice}\times \sqrt{2gh}

Now we know that

C_{d}=\frac{Q_{act}}{Q_{th}}

Thus using this relation we obtain

Q_{act}=C_{d}\times A_{orifice}\times \sqrt{2gh}

Now we know by definition of discharge

Q_{act}=\frac{d}{dt}(volume)=\frac{d(lbh)}{dt}=Lb\cdot \frac{dh}{dt}

Using the above relations we obtain

Lb\times \frac{dh}{dt}=AC_{d}\times \sqrt{2gh}\\\\\frac{dh}{\sqrt{h}}=\frac{AC_{d}}{Lb}\times \sqrt{2g}dt\\\\\int_{1.5}^{0}\frac{dh}{\sqrt{h}}=\int_{0}^{t}\frac{0.62\times 0.3}{15\times 9}\times \sqrt{2\times 9.81}\cdot dt\\\\

The limits are put that at time t = 0 height in pool = 1.5 m and at time 't' the height in pool = 0

Solving for 't' we get

\sqrt{6}=6.103\times 10^{-3}\times t\\\\\therefore t=\frac{\sqrt{6}}{6.103\times 10^{3}}=401.35seconds.

4 0
3 years ago
6. At a construction site, cement, sand, and gravel are used to make concrete. The ratio of cement to sand to gravel is 1 to 2.4
S_A_V [24]

Answer:

Mass of cement used is 62.5 lb

Mass of gravel used is 225 lb

Explanation:

The ratio given here is cement to sand to gravel = 1 : 2.4 : 3.6

So, for 150 lb of sand

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\frac{C}{S}=\frac{1}{2.4}\\\Rightarrow C=S\frac{1}{2.4}\\\Rightarrow C=150\frac{1}{2.4}\\\Rightarrow C=62.5\ lb

Mass of cement used is 62.5 lb

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Mass of gravel used is 225 lb

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3 years ago
Find the toughness (or energy to cause fracture) for a metal that experiences both elastic and plastic deformation. Assume Equat
PtichkaEL [24]

Answer:

Detailed solution is attached below in three simple steps the problem is solved.

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3 years ago
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