what approach did the farmers of the constitution use to limit the powers of the national government and why was that approach successful

The main approach used to limit the powers of the national government was the designation of different levels of government, and the limitation of their functions.

In the US, the government functions at the local, state and federal level. This was a response to concern in the colonies about giving up all of their individual autonomy in order to join the new state.

Additionally, it limits the power of the national government and ensures that local governments (closer to people) still have a say in legislation.

Finally, it works as a response to the size and variety of the country. Each state and each community has varying needs that cannot always be addressed by national legislation.

It is for these reasons that the levels of government work well in the context of the United States.