# Gravity and Centrifugal Force

*Most recent answer: 09/04/2016*

- Dan (age 16)

Maine

I don't have your exact picture clearly in mid, but I think the key part of your question is about how the little weight pulls on the shaft as it swings around. It's easiest to think of this in the frame rotating along with the shaft. The weight has ordinary gravity (mg) pulling it down plus a centrifugal pseudo-force pulling it out away from the rotation axis. The magnitude of that pseudo-force is mrω^{2}, where m is the mass, r is the distance to the axis, and ω is the angular velocity, 2π/T where T is rotational period. So you have to add those two forces as vectors to see which way the result points. It can either pull that end of the shaft down (at low speed) or up (at high speed).

Mike W.

*(published on 09/04/2016)*