one way of looking at it, the 24fps second ball travels 10 seconds, but the 48fps ball only travels 9... because the second difference in time, has already allowed the 48fps ball to reach its peak, and travel back down, 48 feet. the 48 fps ball will be in the air for 9 seconds while the 24fps will still be for 10. they'll pass
hopefully, this post might be easier to understand and prove right, or wrong.