How did the Fugitive Slave Act cause tensions between northerners and southerners?

It also forced people in northern states to take sides on the issue of slavery.

Explanation:Prior to the passage of the Fugitive Slave Act, northerners could view slavery at a distance; it was a problem to be dealt with by southerners. Abolition was pretty far from a good deal of people's minds.

The Fugitive Slave Act made it a crime not to turn in people suspected of being a runaway slave, so it forced people to take a stand -- either by choosing to follow the law, or, as noted in the Emerson quotation that Mark B posted, to choose to disobey it. Either way, someone was taking a stand on slavery in a way that many people did not have to do in the north prior to 1850.

length of the cultivating season was not a problem of new england agriculture

social contract theory, nearly as old as philosophy itself, is the view that persons' moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they live