Mechanics is the branch of physics that deals with the relationship between matter, force, and energy. It might be the study of the effect of a force on a body such as kinetics, statics, and kinematics, or it might be done on a smaller scale, such as in quantum mechanics.
Mechanics is the mother of all forms of engineering, be it electrical, civil or petroleum. Every engineer or scientist working in these fields has to study mechanics at one stage or another. This result in a high demand for textbooks related to mechanics or mechanical engineering, which in itself results in more opportunities for you to make money by selling or renting.
As there are no drastic changes in mechanics over the years, the contents of your old college textbooks will still be relevant. This provides a great opportunity for those students who are running low on funds, or those professionals who are looking for a copy of their favorite book from university days to find what they are looking for, and that too at a lower price.
So if you have those applied mechanics textbooks from your college days lying around or any other related books, do list them for sale and contribute towards creating better engineers and scientist for the future.