Both words can be used for "people" and for "things" contexts. In some cases, they have similar meaning but they are not interchangeable. I hope this information bellow can be useful.
- EXIGIR: to claim, to demand, to require, to urge, to impose (as obligation or a duty);
- PRECISAR: to need, must , have to, need to;
Keeping the meaning in mind, we can see some examples:
- Michael precisa de uma resposta para esta pergunta.
(Michael needs an answer for this question)
- Michael exige uma resposta para esta pergunta.
(Michael requires an nswer for this question)
- Esta pergunta precisa ser respondida.
(This question needs to be answered)
- Esta pergunta exige uma resposta.
(This question requires an answer)
- Eu preciso do Michael para saber se esta explicação foi clara.
(I need Michael to know if I this answer was clear)
- Eu exijo que o Michael diga se esta explicação foi clara.
(I impose to Michael that he tells me if this answer was clear)
In these examples above, EXIGIR and PRECISAR can be used in similar situations both for people and for things. But they have diferent meanings.
- Sorry my bad English
- I hope I could get the idea when you say "for things" and "for people". If not, please let me know if you need more information.