What are the characteristics of carbon fibre?

What is the minimum number of crewmembers needed when using laser plane equipment?

Goshia [24]

Answer:

two

Explanation:

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8 0

3 years ago

Consider a 1.5-m-high and 2.4-m-wide glass window whose thickness is 6 mm and thermal conductivity is k = 0.78 W/m⋅K. Determine

Bess [88]

Answer:

The steady rate of heat transfer through the glass window is 707.317 watts.

Explanation:

A figure describing the problem is included below as attachment. From First Law of Thermodynamics we get that steady rate of heat transfer through the glass window is the sum of thermal conductive and convective heat rates, all measured in watts:

$\dot Q_{total} = \dot Q_{cond} + \dot Q_{conv, in} + \dot Q_{conv, out}$ (Eq. 1)

Given that window is represented as a flat element, we can expand (Eq. 1) as follows:

$\dot Q_{total} = \frac{T_{i}-T_{o}}{R}$ (Eq. 2)

Where:

$T_{i}$ , $T_{o}$ - Indoor and outdoor temperatures, measured in Celsius.

$R$ - Overall thermal resistance, measured in Celsius per watt.

Now, we know that glass window is configurated in series and overall thermal resistance is:

$R = R_{cond} + R_{conv, in}+R_{conv, out}$ (Eq. 3)

Where:

$R_{cond}$ - Conductive thermal resistance, measured in Celsius per watt.

$R_{conv, in}$ , $R_{conv, out}$ - Indoor and outdoor convective thermal resistances, measured in Celsius per watt.

And we expand the expression as follows:

$R = \frac{l}{k\cdot w\cdot d} + \frac{1}{h_{i}\cdot w\cdot d} + \frac{1}{h_{i}\cdot w\cdot d}$

$R = \frac{1}{w\cdot d}\cdot \left(\frac{l}{k}+\frac{1}{h_{i}}+\frac{1}{h_{o}} \right)$ (Eq. 4)

Where:

$w$ - Width of the glass window, measured in meters.

$d$ - Length of the glass window, measured in meters.

$l$ - Thickness of the glass window, measured in meters.

$k$ - Thermal conductivity, measured in watts per meter-Celsius.

$h_{i}$ , $h_{o}$ - Indoor and outdoor convection coefficients, measured in watts per square meter-Celsius.

If we know that $w = 2.4\,m$ , $d = 1.5\,m$ , $l = 0.006\,m$ , $k = 0.78\,\frac{W}{m\cdot ^{\circ}C}$ , $h_{i} = 10\,\frac{W}{m^{2}\cdot ^{\circ}C}$ and $h_{o} = 25\,\frac{W}{m^{2}\cdot ^{\circ}C}$ , the overall thermal resistance is:

$R = \left[\frac{1}{(2.4\,m)\cdot (1.5\,m)}\right] \cdot \left(\frac{0.006\,m}{0.78\,\frac{W}{m\cdot ^{\circ}C} }+\frac{1}{10\,\frac{W}{m^{2}\cdot ^{\circ}C} }+\frac{1}{25\,\frac{W}{m^{2}\cdot ^{\circ}C} } \right)$

$R = 0.041\,\frac{^{\circ}C}{W}$

Now, we obtain the steady rate of heat transfer from (Eq. 2): ( $R = 0.041\,\frac{^{\circ}C}{W}$ , $T_{i} = -5\,^{\circ}C$ , $T_{o} = 24\,^{\circ}C$ )

$\dot Q_{total} = \frac{24\,^{\circ}C-(-5\,^{\circ}C)}{0.041\,\frac{^{\circ}C}{W} }$

$\dot Q_{total} = 707.317\,W$

The steady rate of heat transfer through the glass window is 707.317 watts.

6 0

3 years ago

A shipment from Earth to Mars contains a 60 gallon [gal] tank filled with an ideal gas. The molecular weight of the ideal gas i

mylen [45]

The ideal gas equation can find the amount of gas lost is 7 mol

Given parameters

The initial and final pressures P1 = 3 atm and P2 = 2.2 atm

The temperature T = 20ºC

Container volume V = 60 gallon

To find

The moles of gas lost

The intentional system of measurements (SI) is a system that determines which are the fundamental units, this allows to carry out calculations and exchange measurements in a uniform way and without errors, let's reduce the magnitudes to the SI system

P₁ = 3 atm (1 10⁵ Pa / 1 atm) = 3 10⁵ Pa

P₂ = 2.2 atm (1 10⁵ / 1 atm) = 2.2 10⁵ Pa

PM = 15.9 g / mol (1 kg / 1000 g) = 15.9 10⁻⁻³ kg / mol

V = 60 gallon (1 m³ / 264.172 gal) = 0.2271 m³

T = 20 + 273.15 = 293.15 K

Ideal gases are gases that have no interactions between them, so they can be described by the equation

PV = n R T

Where P is the pressure, V the volume, n the number of moles, R the ideal gas constant (R = 8.314 $\frac{J}{mol \ K}$ ) and T the temperature.

Let's look for the initial moles, that is, on Earth

n = $\frac{PV}{RT}$

n = $\frac{3 \ 10^5 \ 0.2271 }{ 8.314 \ 293.15}$

n = 27.95 mol

Let's write the ideal gas equation for the two instants let's use subscript 1 for Earth and subscript 2 when the spacecraft is on Tuesday

P₁ V = n₁ R T

P₂ V = n₂ R T

$\frac{P_1}{n_1} = \frac{P_2}{n_2}$

n₂ = $\frac{P_2}{P_1} \ n_1$

n₂ = $\frac{2.2 \ 10^5 }{ 3 \ 10^5} \ 27.95$

n₂ = 20.95 mol

This is the amount of moles left, the moles lost are

n_ {lost} = n₁ -n₂

n_ {lost} = 27.95 - 20.95

n_ {lost} = 7 mol

Using the ideal gas equation we can find the amount of gas lost is 7 mol

Learn more about ideal gas here:

brainly.com/question/6684527

3 0

3 years ago

Nbel2, i dont know where you've been all this time but i hope you arent missing please respond i haves heard from you since may

Evgesh-ka [11]

Answer: I don't know what's going but he or she is probably ok

Explanation:

5 0

3 years ago

Read 2 more answers

Discuss the capabilities that should be provided by a DBMS.

Brums [2.3K]

Answer:

They include;

1. A database backup and recovery system.

2. A good security architecture

3. Concurrent access to the system

4. Data dictionary

5. Data definition

6. Data Manipulation Language

Explanation:

A Database Management system shortened as DBMS is used in the organization, storage, and retrieval of data and files in a database. It makes working with files easy and curbs the duplications that can arise from working with files. The capabilities that should be provided by the DBMS include;

1. A database backup and recovery system: There should be a provision for files to be backed up so as to ease their recovery when lost.

2. A good security architecture: This helps to ensure that only authorized users can get access to files. Integrity is also assured this way.

3. Concurrent access to the system: Multiple users should be able to access files at the same time.

4. Data Dictionary: This is a file that helps in the storage of information on the data in the database.

5. Data Definition: This would ensure that the structure of data is properly spelled out.

6. Data Manipulation Language: such as Sequence Query Language is a programmed language that is used in working on data and files.

Examples of DBMS software include:

MySQL, Microsoft Access, Oracle, PostgreSQL, dBase, FoxPro, etc

8 0

3 years ago