Rule 1: 1. اُضْطُرَّ "to be forced to"
The root is ض-ر-ر, as in ضَرَّ to harm. Its Form VIII is اِضْطَرَّ to compel, with the ت of اِفْتَعَلَ turned into ط after the emphatic ض, exactly as in اِصْطَبَرَ (lesson 96). The verb is nearly always met in the passive: اُضْطُرَّ he was compelled, he had to, imperfect يُضْطَرُّ, participle مُضْطَرٌّ forced, obliged. Before a consonant suffix the twins separate: اُضْطُرِرْتُ I was forced, اُضْطُرِرْنَا we were forced. What one is forced to do follows إِلَى with a noun or verbal noun, or إِلَى أَنْ with the subjunctive.
اُضْطُرَّ أَبِي إِلَى أَنْ يَنْتَقِلَ إِلَى مَدِينَةٍ أُخْرَى.
uḍṭurra abī ilā an yantaqila ilā madīnatin ukhrā
My father was forced to move to another city.
اُضْطُرِرْنَا إِلَى الِانْتِظَارِ فِي الْمَحَطَّةِ سَاعَتَيْنِ.
uḍṭurirnā ila l-intiẓāri fi l-maḥaṭṭati sāʿatayni
We had to wait at the station for two hours.
Consonant suffix ـنَا: no contraction.
كَانَتِ الْأُسْرَةُ مُضْطَرَّةً إِلَى بَيْعِ الْبَيْتِ.
kānati l-usratu muḍṭarratan ilā bayʿi l-bayti
The family was obliged to sell the house.
The participle مُضْطَرٌّ as accusative predicate of كَانَ.
يُضْطَرُّ الْمُسَافِرُونَ أَحْيَانًا إِلَى تَغْيِيرِ الْقِطَارِ.
yuḍṭarru l-musāfirūna aḥyānan ilā taghyīri l-qiṭāri
Travellers are sometimes forced to change trains.