Is there a difference between asking a question with "Would you..." and asking the same question with "Can you..."?
For example,
Would you take the trash out?
Can you take the trash out?
Both can be answered with either "Yes/No" or by actually taking the trash out. Are the questions used in different circumstances? Is one more "correct" than the other?
Often (in American English) both phrases are used interchangeably, but in some contexts the second sentence, "Can you..." is used to determine a person's capability, rather than their willingness to do something.
A person in a loud bar might shout, "Can you hear me?"
Additionally, in some contexts "Would you..." is used to determine a person's willingness to do something without any expectation that the person will view the inquiry as a request. "Would you rather fight 100 duck sized horses, or 1 horse sized duck?"
In both of my examples, substitution would sound odd to a native American English speaker. Saying "Would you hear me?" or "Can you rather...?" will likely result in a confused look from your conversation partner.
The first point to make is that it is the kind of question which cries out for the word 'please'. 'Please would you take the.....' can only be a polite request for someone to remove the bin. It would, in my view, not require a question mark, since it is not a question but a request. 'Can you take the....' could conceivably mean one of two things. It could be another way of saying the same thing as before. In which case adding a 'please', would be helpful. Or it could mean 'Are you capable of taking the......'. In that last case the sentence would require a question mark, as it is not a request but a question.
I have thought again about this. 'Would'is clearly the subjunctive and implies politeness. Therefore you can probably get away without using 'please' if you use 'would', though you might want to say 'Would you be so kind as to remove the waste bin'. It follows the French verb 'vouloir' from which it undoubtedly sprang. The French use the subjunctive - 'veuillez'- in the second-person plural if they want to ask someone politely. It can, though not necessarily, dispense with the need for 's'il vous plait'. I regard 'would' as being almost identical to 'veuillez'. In order to understand English, I often find it helps to refer to the French. The Normans really were influential. Thus, one important difference between 'would' and 'can' is that with the latter 'please' becomes 'de rigeur'.
