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vlabodo [156]
3 years ago
14

7. En la sala de una casa hay una gran ventana de vidrio, por la que se presenta una pérdida significativa de calor; las medidas

de la ventana son 2,5 m x 1,5 m y 2,8 mm de espesor. Hallar la variación de calor en la unidad de tiempo si la temperatura exterior del vidrio es 16°C y la temperatura interior del vidrio es 20°C 8. De un cubo de 1 m de arista de un material X se saca de un horno a 40°C, se quiere saber qué cantidad de calor está radiando al exterior, si el coeficiente de emisividad (e) es 0,8 9. En un laboratorio hay una cantidad de 30 moles de un gas perfecto que sufre expansión isotérmica (temperatura constante). La presión inicial de esta masa de gas es de 20 atmosferas y el volumen es de 12 litros. Al final de la expansión, el volumen es de 50 litros. Por lo tanto, determine: a. La presión final de la masa de gas b. La temperatura que se produce en la transformación 10. Un sistema pasa de un estado a otro, intercambiando energía con el exterior. Calcular la variación de energía interna del sistema en los siguientes casos: a. El sistema libera 300 cal y realiza un trabajo de 700 J b. El sistema libera 300 cal y sobre él se realiza un trabajo de 500 J c. El sistema recibe 400 cal de calor y realiza un trabajo de 250 J
Physics
1 answer:
jonny [76]3 years ago
7 0

Answer:

I DON'T SPEAK TACO BELL!

Explanation:

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A student is throwing a ball. She throws the ball up with her left hand, it passes over her head, and she catches it with her ri
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A heat pump is to be used for heating a house in winter. The house is to be maintained at 70°F at all times. When the temperatur
Anna35 [415]

Answer:

\dot{W_{H} } = 4244.48 Btu/h

Explanation:

Temperature of the house, T_{H} = 70^{0} F

Convert to rankine, T_{H} = 70^{0}+ 460 = 530 R

Heat is extracted at 40°F i.e T_{L} = 40^{0}F  = 40 + 460 = 500 R

Calculate the coefficient of performance of the heat pump, COP

COP = \frac{T_{H} }{T_{H} - T_{L}  } \\COP = \frac{530 }{530 - 500  }\\ COP = \frac{530}{30} \\COP = 17.67

The minimum power required to run the heat pump is given by the formula:

\dot{W_{H} } = \frac{\dot{Q_{H} }}{COP} \\...............(*)

Where the heat losses from the house, \dot{Q_{H} } = 75,000 Btu/h

Substituting these values into * above

\dot{W_{H} } = \frac{75000}{17.67} \\ \dot{W_{H} } = 4244.48 Btu/h

3 0
3 years ago
Use the impulse-momentum theorem to find how long a stone falling straight down takes to increase its speed from 3.7 m/s to 9.90
11111nata11111 [884]
<h2>Time taken is 0.632 seconds</h2>

Explanation:

Impulse momentum theorem is change in momentum is impulse.

Change in momentum = Impulse

Final momentum - Initial momentum = Impulse

Mass x Final velocity - Mass x Initial Velocity = Force x Time

Mass x Final velocity - Mass x Initial Velocity =Mass x Acceleration x Time

Final velocity - Initial Velocity = Acceleration x Time

Final velocity = 9.9 m/s

Initial Velocity = 3.7 m/s

Acceleration = 9.81 m/s²

Substituting

9.9 - 3.7 = 9.81 x Time

Time = 0.632 seconds

Time taken is 0.632 seconds

8 0
2 years ago
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