solution

Air is contained in a vertical piston–cylinder assembly by a piston of mass 50 kg and having a face area of 0.01 m2 . The mass of the air is 4 g, and initially the air occupies a volume of 5 liters. The atmosphere exerts a pressure of 100 kPa on the top of the piston. Heat transfer of magnitude 1.41 kJ occurs slowly from the air to the surroundings, and the volume of the air decreases to 0.0025 m3 . Neglecting friction between the piston and the cylinder wall, determine the change in specific internal energy of the air, in kJ/kg.