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mechanical 數學問題~~~

發問:

an ice block having dimensions of 80cm long, 80cm wide and 1m height is floating horizontally in water. the relative density of the ice block is 0.7 and the density of water is 1,000kg/m^3. find: a: the mass of the ice block b: the volume of the water displaced 會計算的人 請幫幫忙~.~ 更新: In an industrial process, 4000kJ of work needed to compress 5 kg of nitrogen. During compression, 320kJ of heat rejected to the surrounding air.Determine the change in specific internal energy of the nitrogen. 更新 2: 謝謝你~~

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最佳解答:

1.(a) Mass = density x volume = 0.7 x (80 x 80 x 100) g = 448 000 g = 448 kg (b) Since upthrust on ice = weight of ice = weight of water displaced Weight of water displacement = 448g N (where g is the acceleration due to gravity) Mass of water displaced = 448 kg Hence, volume of water displaced = 448/1000 m^3 = 0.448 m^3 2. Using First Law of Thermodynamics dQ = dU + dW but dW = -4000 kJ dQ = -320 kJ hence, -320 = dU - 4000 i.e. dU = (4000-320) kJ = 3680 kJ Hence, change in specific internal energy = 3680/5 kJ/kg = 736 kJ/kg

其他解答:A215E4A2B88AAE64
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