Learn Russian: Мой брат выбросил сломанный стул и разбитый телефон. - My brother threw away the broken chair and the smashed phone.

Сломанный is a past passive participle meaning "broken". It is formed from the perfective verb сломать (to break). Because the verb's infinitive ends in -ать, we drop the -ть and add the suffix -нн-, followed by the standard adjective ending -ый.

Why does разбитый use the -т- suffix instead of -нн-?

Past passive participles use the suffix -т- instead of -нн- when the verb root consists of a single syllable ending in a vowel (such as verbs ending in -ить, -ыть, or -еть). Since the verb here is разбить (to smash), which has the short root би-, we drop the -ть and add -т- to get разбитый.

Are сломанный and разбитый in the nominative case here?

They look exactly like the nominative case, but they are actually in the accusative case! Participles decline just like regular adjectives. Because they describe стул (chair) and телефон (phone) — which are masculine inanimate nouns acting as the direct objects of the verb выбросил (threw away) — their accusative forms are identical to their nominative forms.

Both сломанный and разбитый translate to "broken". What is the difference in usage here?