  Orbital angular momentum (Jo), systemic mass (M) and orbital period (P)
distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W
UMa) systems were investigated. The diagrams of log Jo - log P, log M - log P
and log Jo-log M were formed from 119 CAB and 102 W UMa stars. The log Jo-log M
diagram is found to be most meaningful in demonstrating dynamical evolution of
binary star orbits. A slightly curved borderline (contact border) separating
the detached and the contact systems was discovered on the log Jo - log M
diagram. Since orbital size (a) and period (P) of binaries are determined by
their current Jo, M and mass ratio q, the rates of orbital angular momentum
loss (dlog Jo/dt) and mass loss (dlog M/dt) are primary parameters to determine
the direction and the speed of the dynamical evolution. A detached system
becomes a contact system if its own dynamical evolution enables it to pass the
contact border on the log Jo - log M diagram. Evolution of q for a mass loosing
detached system is unknown unless mass loss rate for each component is known.
Assuming q is constant in the first approximation and using the mean decreasing
rates of Jo and M from the kinematical ages of CAB stars, it has been predicted
that 11, 23 and 39 cent of current CAB stars would transform to W UMa systems
if their nuclear evolution permits them to live 2, 4 and 6 Gyrs respectively.
