[krap101]

Hey guys,

I've been looking around for a way to measure angular velocity on a bb, and it seems like the only way is to use a high speed camera (without something super duper expensive). I have a camera that shoots at 1000fps (really low resolution), and I'm trying to figure out the order of magnitude of the rpm of a bb (revolutions/minute). At 400 fps, and assuming no slip, I come up with 40,640 rps or 2438400 rpm, which seems too high, so the assumption of no slip must not be true. I believe the camera will be able to pick up rotations up to 30-40000rpm, but not 2.5million...

Is there rpm data somewhere on the net?

Thanks


Here's the math.

Assuming no slip, the point of contact is seen as instantaneously at rest, meaning you can see the center of the bb as rotating about that point. That means that the center of mass is moving at 400fps, 121.92m/s, with a lever arm of 3mm, and angular velocity is v/r=> 40640 rps.