Originally Posted by andyroddick's mojo
are all these serves in? Cause you'd definitely have to be serving in the 130s to get a ball in and go through the back fence. maybe even 140s.
This would depend quite highly on the fence (how far back from the court it is, how small the open space is, etc.). I used to hit balls through back fences all the time when I was in high school...almost always when I was hitting hard AND with a good deal of spin. I know that I'm capable of serving in the mid 120's and am usually averaging somewhere in the teens for first serves on a good day, but I doubt I was somehow breaking 130 to 140 back then.
This really isn't that great a question for physics majors though (I was one)...it's more anecdotal and for people who have put lots of balls through fences...