  A model based on simple assumptions about 4-dimensional space-time being
closed and isotropic, and embedded in a 5th large-scale dimension, r,
representing the radius of curvature of space-time, has been used in an
application of Newton's Second Law to describe a system with angular momentum.
It has been found that the equations of MOND used to explain the rotation
curves of galaxies appear as a limit within this derivation and that there is a
universal acceleration constant, ao, with a value, again consistent with that
used by MOND. This approach does not require modification of Newtonian
dynamics, only its extension into a fifth large-scale dimension. The transition
from the classical Newtonian dynamics to the MOND regime emerges naturally and
without the introduction of arbitrary fitting functions, if this 5-dimensional
model is adopted. The paper also includes the derivation of an effect in
5-dimensional orbital dynamics which is in reasonable agreement with the
observed Pioneer Anomaly.
