"We need to slice mushrooms for the salad."
Translation:Нам надо нарезать грибы для салата.
Okay I'm going out on a limb but на was previously used in the context of "for lunch", so I would theorise that "нарезать грибы на салат" might mean that the salad consists of those mushrooms and nothing more, and that the sentence has the nuance that slicing mushrooms is the act of creating a salad.
In contrast, the version with для means that the mushrooms augment the salad.
Hardly a scientific study, but for what it's worth: a quick Google search gives these results: "грибы в салат" - 26,600 (though many are in the context of putting mushrooms into the salad)
"грибы на салат" - 70,700
"грибы для салата" - 5,880
In any case, prepositions often can't be translated directly from one language into another; they're best learned in context. And perhaps this is an example that one shouldn't stress over, anyway; Google finds no examples of 'нарезать грибы в салат/на салат' - and the only 3 examples with нарезать грибы для салата are from... Duolingo pages. :P
same question here. Maybe надо is more about the necessity of doing something (think of "I must -or have to- cut mushrooms to make salad") and нужно about the necessity of having something, aka "I need [to have] mushrooms to make salad"), but I am basically just pulling this out of my .... hat ;-)
so, I got some unexpectedly quick reply when I put the question on the Russian Grammar youtube channel (on a 6-year old video, nonetheless!). You can check it here https://www.youtube.com/watch?v=PR5iOYybOdc&lc=z22ezhzzzvbvglhdsacdp43afmpzm3fwundsqvrdbvxw03c010c.1578247458624212&feature=em-comments (my commenter name there is "Jörg Löhken").
The short of it is that there is really not much of a difference, aka it should be accepted. Surprisingly, the explanation that I attempted in my prior comment was actually useful, but for all intents and purposes and in this particular case, there should not be any distinction, so you were totally right with your question, Duolingo should, at some point, accept нужно as well. They are just a bit slow about it, but let's keep in mind that most of the people there are probably volunteers, and if you take just 5 people asking like us every day, for every language, that is already a sh...load of answers to give and complaints to process.
The focus here is on the result of mushrooms getting sliced rather than us doing the action of slicing them. This means that the perfective should be used.
If, for example, this was about us needing to feel the sensation of a knife cutting through mushrooms, the focus would shift to the action instead of the result. In this case the imperfective would be used.
Надо and нужно are impersonal (subjectless) expressions that take the dative - literally, "to us it's necessary to cut.." Russian often uses these to express feelings, possibility, necessity, and permission.
Мне надо работать. = I need to work. Тебе трудно? = Are you having a hard time? Им нельзя говорить по-английски. = They're not allowed to speak English.
There's a short video about it here:
That's actually a really interesting question. So нарезать can be either imperfective or perfective. The distinction is made by the different stress. The imperfective version stresses the second а, the perfective version stresses the е. And the conjugations are different between the two verbs too. In this particular exercise, it's not clear to me whether the imperfective or perfective version should be used, although the robot seems to pronouncing it as imperfective.
Ok, interesting. Previously I remember the voices stressing the е, but now they stress the second а. I don't fully understand perfective vs. imperfective yet, but I would guess this sentence would most likely be perfective (the point is about the end result of having sliced mushrooms ready for the salad), in which case the way they used to pronounce it was correct, and the current pronunciation is not.
Absolutely. для just means "for". The difficulty with all of this is that "for" has several meanings in English, we don't even think about it because there's the one used for all of them. But in Russian they use different words for different meanings: для, на, за and probably others as well.