Astationary object has no forces acting on it?

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.

How much energy will be transferred to your eardrum while listening to this sound for 1.0 min?

Where should a carbon monoxide detector be mounted?