Refer to Figure 9-18. A #_____ electrode lead and workpiece lead should be used to carry 150 amperes of electricity 75 feet to t
1 answer:
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Answer:
Explanation:
Sean A, B y C vectores coplanares tal que:
,
y
Donde ,
y
son las normas o magnitudes respectivas de los vectores A, B y C, mientras que
,
y
son las direcciones respectivas de aquellos vectores, medidas en grados sexagesimales.
Por definición de producto escalar, se encuentra que:
Asimismo, se sabe que ,
,
,
,
y
. Entonces, las ecuaciones quedan simplificadas como siguen:
Es decir,
Luego, se aplica las siguientes identidades trigonométricas para sumas de ángulos:
Es decir,
Las nuevas expresiones son las siguientes:
Ahora se simplifican las expresiones, se elimina la norma de y se desarrolla y simplifica la ecuación resultante:
Ahora se determina el ángulo de :
La función tangente es positiva en el primer y tercer cuadrantes y tiene un periodicidad de 180 grados, entonces existen al menos dos soluciones del ángulo citado:
y
Ahora, la magnitud de es:
Answer:
The heat loss rate through one of the windows made of polycarbonate is 252W. If the window is made of aerogel, the heat loss rate is 16.8W. If the window is made of soda-lime glass, the heat loss rate is 1190.4W.
The cost associated with the heat loss through the windows for an 8-hour flight is:
For aerogel windows: $17.472 (most efficient)
For polycarbonate windows: $262.08
For soda-lime glass windows: $1,238.016 (least efficient)
Explanation:
To calculate the heat loss rate through the window, we can use a model of heat transmission by conduction throw flat wall. Using unidimensional Fourier law:
In this case:
If we replace the data provided by the problem we get the heat loss rate through one of the windows of each material (we only have to change the thermal conductivities).
To obtain the thermal conductivity of the soda-lime glass we use the graphic attached to this answer (In this case for soda-lime glass k₃₀₀=0.992w/m·K).
To calculate the cost associated with the heat loss through the windows for an 8-hour flight we use this formula (using the heat loss rate calculated in each case):
