Can you do it?

“Can you do x?” often asks no more than do you know how or have the ability to do x. But in some contexts, especially where doing ( or being asked to demonstrate ) x is in immediate prospect, “can you do it?” asks me for a pledge that I will do it.

“Can you sink that putt? I have ten dollars that says no.” The situayion is that I’m facing a twelve foot putt and I’m pretty good at that distance. On the practice green, I normally sink 2 out of three at that range. So there is no question whether I am able to sink a 12 foot. The question and challenge is whether I will sink this one. Do I have $10 worth of confidence in my ability on this one putt? That question has less to do with my ability than with other things, as we all understand.

“Yes, I can do it” is not a relevant reply here. I’ve been challenged to bet that I will. Either I accept ( “Your on” ) or decline ( “no bets” ).
But compare the same question asked over dinner by a novice looking for advice on his poor putting game. That is about my ability and wants an answer such as "Yes, I can. Two things are vital. You must..."