You are right, Sara, it is a bit like splitting hairs. The literal translation of the future simple would be future tense in English, hence on fera un gâteau, unless context dictates something different, is “we will make a cake...”

Hi James, this link ( https://www.francaisfacile.com/forum/lire.php?num=7&msg=77347&titre=Faire+du+tennis+et+jouer+au+tennis ) suggests that it may be a bit of a connotation thing. Jouer au foot means to play, which is more for fun, faire du foot is more like “training?” (I looked this up, because I was sure that one used “au tennis, au foot” - but apparently that’s just when it’s conjugated with “jouer,” - and for “faire” it’s du tennis, du foot. Go figure.)

They also say that faire would more be naturally used for sports in contexts where you’re listing, say, a bunch of hobbies all of which you “do” but not all of which you “play.”

Thank you for the reasoning, which seems very nebulous! I`m certain a French person would know what I meant, but getting marked incorrect in a test spoils my day!

Thanks J,  this is  very helpful. Was confused initially.

Well, even in English there's a slight difference between "are going to" and "will do their homework". In fact, the difference is very similar to the French future proche and future simple. The difference is that future proche is mostly used for things that the speaker considers not too far in the future. Futur simple is for more distant future actions.

Fiona, this is a subtle nuance only which, in some sentences, does make a difference.

For example: My stomach hurts,  I'm going to throw up. You wouldn't use "...I'll throw up" in this context, even though it's grammatically correct.

In many cases either is possible. But the distinction is more prevalent in French than it is in English.

I think they both describe the same situation, but there is a difference in register - the first sentence is more formal.

In the second sentence it sounds to me like the girls have decided to do their homework after lunch; in the first sentence it sounds like they've been told to, or they always do it then.

You might find this document useful to explain some of the differences in usage between the two future tenses in English which seem to be roughly the same in French:

https://www.laits.utexas.edu/tex/pdf/taf4.pdf

Hi Arndís,

I agree with Alan in that there is slight difference in register between, e.g.:

Je vais te dire. -- I am going to tell you.
Je te dirai. -- I'll tell you.

In addition, it seems that there is also slight different in temporal proximity. La future proche (Je vais te dire) is slightly closer to the present than la future simple (Je te dirai).

-- Chris