Some dragonflies splash down on the surface of a lake and then fly upward, spinning rapidly to spray the water off their bodies. When the dragonflies spin, they tuck themselves into a "ball."
They spin with a linear speed of $2.3 \mathrm{~m} / \mathrm{s}$ and produce a centripetal acceleration of $250 \mathrm{~m} / \mathrm{s}^{2}$. What is the radius of the ball they form?