  We consider a set of macroscopic (classical) degrees of freedom coupled to an
arbitrary many-particle Hamiltonian system, quantum or classical. These degrees
of freedom can represent positions of objects in space, their angles, shape
distortions, magnetization, currents and so on. Expanding their dynamics near
the adiabatic limit we find the emergent Newton's second law (force is equal to
the mass times acceleration) with an extra dissipative term. In systems with
broken time reversal symmetry there is an additional Coriolis type force
proportional to the Berry curvature. We give the microscopic definition of the
mass tensor relating it to the non-equal time correlation functions in
equilibrium or alternatively expressing it through dressing by virtual
excitations in the system. In the classical (high-temperature) limit the mass
tensor is given by the product of the inverse temperature and the Fubini-Study
metric tensor determining the natural distance between the eigenstates of the
Hamiltonian. For free particles this result reduces to the conventional
definition of mass. This finding shows that any mass, at least in the classical
limit, emerges from the distortions of the Hilbert space highlighting deep
connections between any motion (not necessarily in space) and geometry. We
illustrate our findings with four simple examples.
