TOPIC: Quick vs Fast

I came across the following dialog.
A: Can I steal a minute of your time ?
B: Sure. But be quick, OK?
Can I use 'fast' instead of 'quick' ? If yes, what's the difference between the two?

A: Can I steal a minute of your time?
B: Sure. But be quick, OK?
In many instances, like B above, for example, “fast” and “quick” can be used interchangeably to mean rapidly. However, there are definite differences in meaning in other instances. The Merriam Webster Online Dictionary (www.m-w.com) says that FAST applies particularly to things that move (e.g., “fast horses”,“a fast train”), and QUICK suggests promptness and the taking of little time (e.g., “a quick dinner”, “quick thinking”).
I suggest you study some of the entries for these two words at that site or at one of the other online dictionary sites, comparing the examples of use in particular. It would also be a good idea to look at some of the collocations for each word at this site: www.edict.com.hk/default.htm. Studying the examples of use will help you learn which one to use in which situation.