In air, you'd call it air resistance, pilots call it drag. In water, some call it
water resistance, or just plain drag.
Whatever it's called, it's the friction between the object and the fluid, plus
the force needed to push the fluid out of the way to let the object get through.
Work is performed while initially lifting books off the floor. The work is due to gravity.
Acid's release protons, or hydrogen ions.
Hope this helped, have a great day! :D
The answer is gravity my friend. :
)