Centripetal Forces: 1) How does a common market unite Europe?
2) How does the creation of an EU trading bloc unite Europe?
Centrifugal Forces:
1) How do the differences between western and eastern nations divide the EU?
2) What divisions are created by the use of the euro?

1, 2: there are no taxes on brought in gods, the money, the workforce and the goods can stream within the borders of the EU freely and in this way the whole EU is more competitive in an international level

3,4:the western part of the EU more developed due to the inherited capitalist economy and Marshall plan by the USA, while the post communist more backward because of the ex communist industrial economy and because of the fact that they had to change to capitalist

Not all the countries have euro within the EU just the more developed nations with few exceptions like Sweden and therfore the EU is not united in this front as well