I want to do the following vertical circular motion experiment, where I "hand spin" a rotating mass (red) that is attached to the same string with the slotted mass at the other end. I spin the mass by grabbing the hollow tube (blue).
My question is what would happen to the velocity of the rotating mass? Would rotating mass adopt constant angular velocity? Why or why not? Based on observation, it seems to me that if a lighter rotating mass was used, it does somewhat adopts constant angular velocity. Why is that?
If the rotating mass does not adopt constant angular velocity, would that mean the velocity changes at every point? And the velocity of the rotating mass would be the highest at the bottom of the circle( $u \geq \sqrt{5gr}$) and lowest on top of the circle ( $u\geq \sqrt{gr}$)?
And for calculations, can I just use minimum velocity (ie use $u = \sqrt{gr}$ as the velocity on top)?