How do you find out how fast an object will fly through the air?
They sell radar guns (I'm not sure if that's what they really call them) at Sports Authority. Probably any other sporting goods store may carry them too. I had seen them by the baseball stuff.
With one of those police things that are like radar guns or whatever to catch people who are speeding. Or is that just in the movies?
Throw it and guess
stand in front of it