Question

Part A) Two identical pieces of machinery are lifted from the sidewalk to the roof of a 100.0 m tall building. One is lifted directly to the building's roof and has a change in internal energy of 1059 kJ. The other is lifted to twice the height of the building and then lowered to the roof. What is the change in internal energy of the second piece of machinery once it has reached the roof?

Part B) As a reaction occurs, the system loses 1150 J of heat to the surroundings. A piston moves downward as the gases react to form a solid. As the volume of the gas decreases under the constant pressure of the atmosphere, the surroundings do 480 J of work on the system. What is the change in the internal energy of the system?​

Part C) Calculate the change in the internal energy of the system for a process in which the system absorbs 140 J of heat from the surroundings and does 85 J of work on the surroundings.​

Answer 1

Part A )

the internal energy becomes twice.

Part B)

system loses heat Q = 1150 J

work done on the system = 480 J

change in internal energy U = Q + W

                                             = - 1150 + 480

                                             = - 670 J

change in internal energy U = - 670 J

Part C)

heat absorbed Q = 140 J

work done by the system = 85 J

internal energy change U = q + W

                                         = 140 - 85

                                         = 55 J

internal energy change U = 55 J