[unleash10]

I was wondering why cant we have a situation where the equation for work as w = change in P times constant volume.
EG we have a piston with a changing external pressure being applied but the volume is not changing because the work from the system is adjusting to the change in external pressure.

[Yggdrasil]

Mechanical work cannot be done without there being motion.  If volume doesn't change, then there is no macroscopic motion causing mechanical work do be done on the system.