Farther vs. Further - Writing tip of the day

I believe there is a scene in Finding Forester that will further clarify the distinction between the two words.

Farther: deals strictly with physical distance

The car chase went much farther then excepted and ended in a fiery mess.

Further: usually deals with metaphorical distance but can also be used for physical distance.

I can not go any further, I feel like I am going to puke.