Breakdown of Slušaš li meteorologa kada planiraš izlet?
li
question particle
slušati
to listen
izlet
trip (m)
kada
when / if (with conditional)
Questions & Answers about Slušaš li meteorologa kada planiraš izlet?
Why does meteorologa have an -a at the end, but the other direct object, izlet, does not?
Both are masculine nouns in the Accusative case, but Croatian distinguishes between animate and inanimate masculine nouns. Because meteorolog is a person (animate), its Accusative takes the -a ending. Because izlet (trip) is an inanimate concept, its Accusative form stays identical to the Nominative.
How would I change this sentence to say 'when you plan tomorrow's trip' using the temporal adjectives from this lesson?
You would use the adjective sutrašnji (tomorrow's) and place it right before the noun, making it kada planiraš sutrašnji izlet. Since izlet is masculine inanimate, the adjective also takes the inanimate Accusative form, which is identical to the Nominative.
Could I start this sentence with Da li slušaš instead of Slušaš li?
Could I use the perfective verb isplaniraš instead of planiraš here?
It would change the nuance. Using the imperfective planiraš asks about a general habit: 'whenever you are in the process of planning a trip'. If you used isplaniraš, it would focus on the completion of the planning, usually for a specific, single trip.