Is that not moment of inertia?
The idea is to have an equation that works out the torque required to rotated the vertical disk. It must include the coeficient of friction between the surfaces of the disk/window as one of the variables. I assume the torque needed to overcome the friction...
Thanks for the response but my maths is extremely rusty. I understand the general concept of your response but what would the exact formula look like when complete so that i could use it?
Ive been trying to find formulas that help describe the torque needed to rotate a flat disk on a flat surface when the coefficient of friction between the 2 materials is known.
The first surface is a glass window (so a vertical plane) the second surface is a rotating disk of wet sponge...