  A Collective coordinate variable for adding a space dependent potential to
the sine-Gordon model is presented. Interaction of solitons with a delta
function potential barrier and also delta function potential well is
investigated. Most of the characters of interaction are derived analytically.
We will find that the behaviour of a solitonic solution is like a point
particle which is moved under the influence of a complicated effective
potential. The effective potential is a function of the field initial
conditions and also parameters of added potential.
