Whether vs If

[Armstrong]

please what's the ideal circumstance to use "if" and "whether"?
For instance, if i want to say:

"I'd like to know sir if you would be coming later today."

or

"I'd like to know sir whether you would be coming later today."

???

Thank You.

[Yankee]

Hi Armstrong
There was a question in the forum about if and whether just a few hours ago:
http://www.english-test.net/forum/ftopic24181.html#80985

In your sentence, you can use either if or whether.
However, it would be better to say "will be coming" (not "would be coming").
.