A rough platform $\mathrm{OA}$ rotates in a vertical plane about a horizontal axis through the point $\mathrm{O}$ with a constant counterclockwise velocity $\mathrm{\omega }=3 \mathrm{rad} {\mathrm{s}}^{-1}$. As it passes through the position $\mathrm{\theta }=0$, a small mass $\mathrm{m}$ is placed upon it at a radial distance. If the mass is observed to slip at $\mathrm{\theta }=37°$, then the coefficient of friction between the mass & the member is