"Force or fear" is the dividing line.
A purse lifted without any resistance is generally not robbery. The same purse taken after a struggle is. That difference is the whole case, because force or fear is the only thing separating robbery from theft. Picking something up and carrying it off is not force, however fast it happens. The force has to be more than the taking itself required: enough to overcome someone holding on to their property, or to make them let go.

