Using "would" to make questions

Affirmative: She would be at John's place.

Negative: She wouldn't be at John's place.

Will the question sentence be "Would she be at John's place?"?

Please enlighten me on this. Thank you very much!

Grammar Geek

But how do you anticipate using these? If she had her choice, she would be at John's place. Something like that?

I was trying to use the "would" to express possibility. So I came up with these three sentences. It's like "A: Do you know where she is? B: She would (=may/might) be at John's place.".

No.

She COULD be at John's place.

She WOULD be at John's place if... [something]

Actually one of my grammar books says "would" can be used to suggest "possiblity", so I thought that it could have the same meaning of "may/might", which suggests "possiblity".

If "would" cannot be used to suggest "possiblity" like may/might does, then what does the "would" mean in the following sentences? (All these sentences are from the book I mentioned above)

▲"Who is the man you want to speak to?"  "You wouldn't know him." (Shouldn't it mean the same thing as may/might not?)

▲It is estimated that a round-trip flight to Mars would take more than a year and a half. (Shouldn't it mean the same thing as may/might? Or this "would" is only a substitute of "will"?)

▲It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year would be greater than the total weight of all the human beings in the country. (Shouldn't it mean the same thing as may/might?Or this "would" is only a substitute of "will"?)

The book also says "would have done" suggests "past possibilities", if "would" cannot be used to suggest "possiblity" like may/might does, then nethier will be "would have done". If  "would have done" cannot be used to suggests "past possibilities",  what would the "would have done" in the following sentences mean?

▲He would have reached New York.  (Shouldn't it mean the same thing as may have reached/might have reached?)

▲I thought you would have finished this by now.  (Shouldn't it mean the same thing as may have finished/might have finished?)

Please give me your opinion about this, thanks again!

would doesn't mean possible in the same way that may and might do.  would is actually more definite, more certain, than may or might, because if you say something may be true, it means maybe it's true, and maybe it's not true.  would doesn't work that way.  would is probably the most difficult word in English to explain!

You wouldn't know him. (~ My guess is that you probably don't know him. ~ I strongly doubt that you know him. ~ There is nothing that leads me to think that you know him.) 

 A flight to Mars would take more than a year.  (In an imaginary world where flights to Mars are ordinary events, a flight to Mars takes more than a year.)  [This is a different usage from the usage in the first sentence.]

The weight of insects ... would be greater than the weight of ....  (In an imaginary world where we are able to make such measurements, the weight of insects ... is greater than the weight of ....)  [Same usage as in the second sentence.]

He would have reached New York. (In an imaginary world where certain conditions were met, he reached New York.)

I thought you would have finished this by now.  (In an imaginary world - the imaginary world created by my thoughts - you have already finished this.)

My paraphrases are only approximate.  There is no real definition of would.  You just need to hear it and imitate it a lot before you start to understand how to use it.  A clause with would is most often accompanied by an if clause that reveals more about the imaginary world we are in by expressing a condition.

CJ