(a) why did the farmers consider it necessary to replace the articles of confederation? (b) what obstacles did they face in creating a strong central government?

They believed that it was necessary because they needed a strong central government and the articles did not provide for that. The government had very little power according to the articles so they wanted to make a new constitution. The obstacles they met were from the anti-federalists who were a group of people who believed state rights and individual rights should be more important and should be protected from a strong central government.

The answer is ethnic groups.