Speed Trap for Thrown Object

[Penth]

So long story short, we began arguing at work about who could throw certain objects fastest and now I'd like to build a sensor system to do so. Anyone have suggestions for what sensors I should consider for this delicate timing operation.

I have considered using a long box with a PIR sensor at each end, with their fields narrowed so as to only trigger when the object passes through the openings, that will start and stop a timer giving me the time the object traveled over a known distance and allowing me calculate the velocity of the object.

Putting the sensors on hardware interrupts should give me fairly accurate readings if the sensors are consistent in triggering the interrupt.
Has anyone tried high speed measurements and what sensors did you use?

[sonictj]

you could set up two arrays of IR emitters and detectors each going to a large or gate to create  "break planes" from break beams this gives you two switches that are very fast.  Then compare the time between the object passing the first break plane and the second.  If you do this inside you don't have to worry about sunlight.