Here are some interesting links:

[url=http://www.jayandwanda.com/tt/ballspeed_calc1.html]http://www.jayandwanda.com/tt/ballspeed_calc1.html[/url]
[url=http://www.jayandwanda.com/tt/ttb_calc.html]http://www.jayandwanda.com/tt/ttb_calc.html[/url]
[url=http://www2.physics.umd.edu/~mfuhrer/course/spr02/AJP/AJP00482.pdf]http://www2.physics.umd.edu/~mfuhrer/course/spr02/AJP/AJP00482.pdf[/url]
[url=http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/10242/32662/01530584.pdf?arnumber=1530584]http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/10242/32662/01530584.pdf?arnumber=1530584[/url]