its just Em G A and D throughout the whole song. or at least thats what i thought it 
like. my first tab anyway. it sounds pretty accurate. Maybe not so for the A part but its alright..

Flo Rida)

Em           G                    D
You spin my head right round, right round


                         A
When you go down, when you go down down


(Katy Perry)
Em           G                    D
You spin my head right round, right round


                         A
When you go down, when you go down down