A bucket filled with water is tied to a rope of length 0.5 m and is rotated in a circular path in vertical plane. The least velocity it should have at the lowest point of circle so that water does not spill is. $(g=10ms^{-2})$

Question

$$\begin {array} {1 1} (a)\;\sqrt 5 m/s & \quad (b)\;\sqrt {10} m/s \\ (c)\;\sqrt 5 m/s & \quad (d)\;2 \sqrt 5 \end {array}$$