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iVinArrow [24]
3 years ago
5

Special considerations must be given to systems using liquid hydrogen for fuel because of: A. Liquid hydrogen's low density B. L

iquid hydrogen's low storage temperature C. The high flammability of hydrogen vapors D. All of the above
Engineering
1 answer:
vitfil [10]3 years ago
6 0

Answer:

D.All of the above

Explanation:

Properties of hydrogen:

1.It is lighter than air.It has density about 0.089 g/L.

2.Hydrogen  rapidly change from liquid state to gas,so special protection is required to protect it.

3.It is highly flammable gas.

4.Liquid form of hydrogen exits at -432 F .This is very low temperature so special protection requires to keep it in liquid form.          

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Precast double-tee units are generally used as structural floors when:________.
TiliK225 [7]

Answer:

<em>d. floor spans exceed that which is economical with site-cast or hollow-core slabs and exceed 60 feet.</em>

<em></em>

Explanation:

<em> Double tee slabs are prestressed concrete castings usually about 100 m to 150 m long</em>. <em>They are usually used in the construction industry in structures requiring a long floor span (or roof span) exceeding 60 feet in length, that is required to bear additional load (additional load carrying capability</em>). Double tee slabs are usually employed in construction because they shorten construction time. reduce congestion at the construction site, and also reduce construction cost.

<em>They are the required choice in construction when the cost of site casting or hollow-core slabs is no longer economical due to the length of the structure exceeding 60 feet.</em>

8 0
3 years ago
The 5-kg collar has a velocity of 5 m&gt;s to the right when it is at A. It then travels along the smooth guide. Determine its s
Gnoma [55]

Answer:

The speed at point B is 5.33 m/s

The normal force at point B is 694 N

Explanation:

The length of the spring when the collar is in point A is equal to:

lA=\sqrt{0.2^{2}+0.2^{2}  }=0.2\sqrt{2}m

The length in point B is:

lB=0.2+0.2=0.4 m

The equation of conservation of energy is:

(Tc+Ts+Vc+Vs)_{A}=(Tc+Ts+Vc+Vs)_{B} (eq. 1)

Where in point A: Tc = 1/2 mcVA^2, Ts=0, Vc=mcghA, Vs=1/2k(lA-lul)^2

in point B: Ts=0, Vc=0, Tc = 1/2 mcVB^2, Vs=1/2k(lB-lul)^2

Replacing in eq. 1:

\frac{1}{2}m_{c}v_{A}^{2}+0+m_{c}gh_{A}+      \frac{1}{2}k(l_{A}-l_{ul})  ^{2}=\frac{1}{2}m_{c}v_{B}^{2}+0+0+\frac{1}{2}k(l_{B}-l_{ul})  ^{2}

Replacing values and clearing vB:

vB = 5.33 m/s

The balance forces acting in point B is:

Fc-NB-Fs=0

\frac{m_{C}v_{B}^{2}   }{R}-N_{B}-k(l_{B}-l_{ul})=0

Replacing values and clearing NB:

NB = 694 N

6 0
4 years ago
Read 2 more answers
Why metals are good thermal conductors, but polymers are not?
jok3333 [9.3K]

Answer: Metals are good thermal conductors because they have close packaged metal ions in their lattice structure but in polymers they have discontinuous structure which make them poor as a conductor.

Explanation: Metals are considered as good thermal conductors because of their lattice structure which has tightly packed ions in it. In the outer shell of atoms the electrons are free to move and thus conduct the electricity but for the polymers, they have a different structure as compared to metals thus it makes it difficult for a polymer to conduct electricity due to high number of discontinuous particle chains. Therefore metals are good conductors , but polymers are not.

4 0
4 years ago
\o you sell them?” "Fivepence farthing for one—Twopence for two,” the Sheep replied. "Then two are cheaper than one?” Alice said
NemiM [27]

Answer:

unusual and strange

Explanation:

3 0
3 years ago
Steam at 40 bar and 500o C enters the first-stage turbine with a volumetric flow rate of 90 m3 /min. Steam exits the turbine at
a_sh-v [17]

Answer:

(a) 62460 kg/hr

(b) 17,572.95 kW

(c) 3,814.57 kW

Explanation:

Volumetric flow rate, G = 30 m³ / 1 min => 90 / 60 => 1.5

Calculate for h₁ , h₂ , h₃

h₁ is h at P = 40 bar, 500°C => 3445.84 KJ/Kg

Specific volume steam, ц = 0.086441 m³kg⁻¹

h₂ is h at P = 20 bar, 400°C => 3248.23 KJ/Kg

h₃ is h at P = 20 bar, 500°C => 3468.09 KJ/Kg

h₄ is hg at P = 0.6 bar from saturated water table => 2652.85 KJ/Kg

a)

Mass flow rate of the steam, m = G / ц

m = 1.5 / 0.086441

m = 17.35 kg/s

mass per hour is m = 62460 kg/hr

b)

Total Power produced by two stages

= m (h₁ - h₂) + m (h₃ - h₁)

= m [(3445.84 - 3248.23) + (3468.09 - 2652.85)]

= m [ 197.61 + 815.24 ]

= 17.35 [1012.85]

= 17,572.95 kW

c)

Rate of heat transfer to the steam through reheater

= m (h₃ - h₂)

= 17.35 x (3468.09 - 3248.23)

= 17.35 x 219.86

= 3,814.57 kW

8 0
3 years ago
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