A ball rolls off the top of a stairway with horizontal velocity u. The steps are 0.1 m high and 0.1 m wide. The minimum velocity u with which that…

A ball rolls off the top of a stairway with horizontal velocity $\displaystyle u$. The steps are $\displaystyle 0.1$ m high and $\displaystyle 0.1$ m wide. The minimum velocity $\displaystyle u$ with which that ball just hits the step $\displaystyle 5$ of the stairway will be $\displaystyle \sqrt{x} m s^{-1}$ where $\displaystyle x=$ $\displaystyle \_\_\_\_$ $\displaystyle \left[\right.$ use $\displaystyle \left.\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right]$.