A sealed piston-cylinder assembly initially contains a gas at temperature T, pressure P , and volume . The piston has a mass m, a cross-sectional area A, and its top surface is subjected to atmospheric pressure. The gas undergoes a heating process and reaches equilibrium state a new characterized by a temperature T, pressure P, and volume V. piston mass: m cross-sectional area: A Paim T,U, P, State 1 heating P atm T, U, P 2' State 2 By writing a force balance for the piston at each state, demonstrate that the gas pressure remained constant during the heating process.