Most FB's aren't strait-away bullet spin.
I think if you are chucking one 60+ with reasonable spin rate (15+),
that ball is going to move, at least a little.
She mentioned to me she recently noticed the ball seem to rise and then drop as it is approaching the plate. I thought I was seeing the same thing, but then again, I am a newbie and know nothing about this. Is that possible?
CORRECTION: I had earlier said 75 rps was about the spin needed for the ball to rise above its initial plane, assuming 70 mph release speed. I messed up (yes, even physicists do that, more often than you think; but, we are very good at finding our mistakes). It is more like 60 rps, still about twice what RevFire gives for elite players. The numbers for the spin in the slides I posted earlier are not my own numbers. The PITCHf/x system does not measure the spin. It measures the movement and used that to infer the spin, with the aid of a model. I don't recall offhand whether the model that is used is the best one available, so the absolute numbers for spin should be taken with a grain of salt. The numbers for movement are much more reliable.
I don't know what that means.
actually, to properly clarify, it's "RPS" (revolutions per second).
RPM (Oops! Should be RPS! Thanks corlay!)