# Inertia and equlibrium of machines

1. Sep 19, 2008

well, i would like to ask abt sth we studied in theory of machines ' we studied chapter named(equilibrium of machines) but i am really so confused abt concept of this equilibrium
because in this chapter we have studied that any part of machines under equlibrium
u can apply these equations to it
(1)f=ma
where f is inertia force
(2)inertia torque=mass x angular acceleration
and i think for any object under any forces u can apply newton's second law on it
total forces= ma where (ma is the inertia force) so i understand from this equation that this part of machine comes to equilibrium due to its inertia force
well,my question here is that every object is under inertia force when some forces acts on it so any part of machine will be in equilibrium even without calculations i know this maybe wrong but i cant find interpretation

this maybe because i have misunderstanding abt concept of equilibrium like sometimes iam asking when part of machine not in equilibrium ?what happens to it if it's not in?sth like that
or maybe i ve problem abt concept of inertia force or inertia torque

but really i am so confused abt the equations above every object or every part of machine will be in equlibrium ???even without calculations???