A gas is contained in a vertical piston-cylinder assembly by a piston with a face area of 40 in² and weight of 100 lbf. The atmosphere exerts a pressure of 14.7 lb/in² on top of the piston. A paddle wheel transfers 3 Btu of energy to the gas during a process in which the elevation of the piston increases slowly by 3 ft. The piston and cylinder are poor thermal conductors, and friction between the piston and cylinder can be neglected. Determine the work done by the gas on the piston, in Btu, and the change in internal energy of the gas, in Btu.

A gas is contained in a vertical piston-cylinder assembly by a piston with a face area of 40 in² and weight of 100 lbf. The atmosphere exerts a pressure of 14.7 lb/in² on top of the piston. A paddle wheel transfers 3 Btu of energy to the gas during a process in which the elevation of the piston increases slowly by 3 ft. The piston and cylinder are poor thermal conductors, and friction between the piston and cylinder can be neglected. Determine the work done by the gas on the piston, in Btu, and the change in internal energy of the gas, in Btu.