Well, I would say that the collision causes the shock.
They are one and the same thing, but both part of a process which their existence relies upon.
The shock is the culmination and result of the forces which led to the collosion.
However I'm not of a mechanical mind and you could be using the terms in a very specific, technical way of which I am not aware.
It is difficult to judge the sentence you have presented without having an idea of the context.