Just about everyone has stood on the side of the road as cars fly by at 60 or 70 mph right?

But how many of us have ever had something coming at us at 135 mph?

In the second round of the men's singles at the US Open Tennis Competition today Andy Roddick  was serving to opponent Kristian Pless at 135 mph.

How fast is too fast?

What is the fastest ball you think an average person could react to? (Let alone return.)

Remember: F=M x V