All due respect, you're speculating on the object size, material, and shape totally. I'm thinking the velocity was quite good for you to hear it over the mower engine, radio, engine noise.... Careful you don't shoot your eye out with that Daisey Red Ryder...:facepalm:0.2 grams at 30f distance by the speed that the propeller was doing I'm guessing a pretty hefty exit speed but the lack of weight plus the bad aerodynamics of the object in question (not counting air fluid resistance since should be almost meaningless) must have slowed the crap down of that thing by the time it reached my passenger door.
I barely herd like loose sand hitting the door, not even an impactPaint is not that good.