Matter accreting onto black holes may develop shocks due to the centrifugal barrier .
A part of inflowing matter in the post-shock flow is deflected along the axis in the form of jets .
Post-shock flow which behaves like a Compton cloud has ‘ hot ’ electrons emiting high energy photons .
We study the effect of these ‘ hot ’ photons on the outflowing matter .
Radiation from this region could accelerate the outflowing matter but radiation pressure should also slow it down .
We show that the radiation drag restricts the flow from attaining a very high velocity .
We introduce the concept of an ‘ equilibrium velocity ’ ( v _ { eq } \sim 0.5 c ) which sets the upper limit of the terminal velocity achieved by a cold plasma due to radiation deposition force in the absence of gravity .
If the injection energy is E _ { in } , then we find that the terminal velocity v _ { \infty } satisfies a relation v _ { \infty } ^ { 2 } \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } v _ { eq } ^ { 2 } +2 E _ { in } .