It's a bit of a shame this is buried in the "beef" thread... it's really quite generalized now! Anyway...
LIB: It only matters when one is doing force and torque balances, in an attempt to figure out what the other forces in the system are... One can only consider "real" forces on a body for those, or they will quickly get tripped up into thinking they've found anomolies that the real world doesn't seem to support.
Jim,
"There is a force which the string exerts on the body. And there is a force which the body exerts on the string. But there is no force radially outward on the body."
You're misunderstanding this a bit. You're obviously correct about equal and opposite forces. Since the string is pulling inward on the body (to keep it from traveling in a straight line; accelerating it toward the center constantly), the body is, in turn, pulling outward on the string. This is obvious if you view each part in isolation, which is what the free-body diagram is- draw any portion of a machine, and anywhere you cut it, you can draw in forces and solve for their values with torque and force balances such as F=mA, T=I*alpha (for rotational torque), or (if you're lucky enough to not have any acceleration in any given direction) F = 0 and T = 0.
So cut the rope and draw the ball by itself and you'll only see gravity and the rope force, pulling the body inward. The F=mA for this requires the horizontal component of rope tension to create the inward acceleration. Now draw the rope only- you can obviously use the rope force value, but you'll need to point it in the other direction- the ball is pulling on the rope! That's all that Professor Miller is talking about.
I'm just trying to dispel the false concept that centrifugal force is not a real force. It is a very real force.
I hope you're right- then when your theory is proven, I can say I had a lively technical discussion with one of the greatest technical minds of the century! I'm in no position to argue; I can only parrot what they fed me in my Physics and Engineering classes, which makes sense to me, and seems to be capable of solving all the dynamics problems I've seen to this point.
And aren't we looking for some magical force to appear and power our PM wheels?
Ahhh yes- the crux of the matter. I warned of this in my very first or second posting- if one follows the current wisdom verbatim, it can only point to the futility of the effort. Maybe I'm not the best person to have this discussion with- I'm hoping there is something that Newton missed, which is why I'm here at all. But in that respect, I shouldn't be pointing to Newtons equations and telling you how things must work! I wish you nothing but good luck in your quest! Maybe lurking is a better approach, so I don't discourage everyone...
-Kevin