I'm reading Yotsubato to learn Japanese. On page 98 of Tome 1, Asagi asks Yotsuba:

> クーラーって　知ってるかなー？

I understand she's asking if Yotsuba knows what an air conditioner is, but I'm unsure about the nuance brought by the use of か and なー here. 

From [Tae Kim's guide][1],

> The question marker 「か」 is usually not used with casual speech to make
> actual questions. It is often used to consider whether something is
> true or not. Depending on the context and intonation, it can also be
> used to make rhetorical questions or to express sarcasm. It can sound
> quite rough so you might want to be careful about using 「か」 for
> questions in the plain casual form.

So which is it here? I'm pretty sure she's not trying to sound rough or sarcastic.

Also, is なー　here just a way of saying な, itself just a way of saying ね (I'm still quite confused with all the sentence-ending particles)? What would be overall an accurate translation of the question?


  [1]: http://www.guidetojapanese.org/learn/grammar/question