  Making use of the classical Binet's equation a general procedure to obtain
the gravitational force corresponding to an arbitrary 4-dimensional spacetime
is presented. This method provides, for general relativistic scenarios,
classics expressions that may help to visualize certain effects that Newton's
theory can not explain. In particular, the force produced by a gravitational
field which source is spherically symmetrical (Schwarzschild's spacetime) is
obtained. Such expression uses a redefinition of the classical reduced mass, in
the limit case it can be reduced to Newton's Universal Law of Gravitation and
it produces two different orbital velocities for test particles that
asimptotically coincide with the Newtonian one. PACS: 04.25.Nx, 95.10.Ce,
95.30.Sf. Keywords: Universal gravitational law, perihelionshift, Schwarzschild
potential, reduced mass.
