$9\mathrm{.}3\mathrm{.}49$ A $0\mathrm{.}30-$m$-$diameter cork ball $)$ is tied to an object on the bottom of a river as is shown in Fig. P$9\mathrm{.}3\mathrm{.}49.$ Estimate the speed of the river current. Neglect the weight of the cable and the drag on it$.$

FIGURE P$9\mathrm{.}3\mathrm{.}49$