Well, if you agree that physical violence is application non-consensual force, then it works out fine, since then any force applied without warning is an violent act.

I think its a fine definition of violence, IF you accept that violence is sometimes necessary (I think most people hold this view), or even that violence may not be inherently wrong (really a logical extension of the first... but I feel that less people would say they agree with this view).

Non-consensual force is enslavement, not violence. In my view any reasonable definition of violence has to involve injury of some kind.

Um, I think of violence as application of force to cause lasting or permanent injury or death.

Slapping someone in the face is definitely a violent act, in most cases though, it won't cause any lasting or permanent injury and definitely not death(unless you are the hulk or something).

Why? it seems to be just a matter of scale.