$\mathbf{}$ - (a) Derive an equation for the radial acceleration that includes $v$ and $\omega$, but not $r$. (b) You are designing a merry-go-round for which a point on the rim will have a radial acceleration of $0.500 \mathrm{~m} / \mathrm{s}^{2}$ when the tangential velocity of that point has magnitude $2.00 \mathrm{~m} / \mathrm{s}$. What angular velocity is required to achieve these values?