A ball rolls off top of a staircase with a horizontal velocity `u m s^-1`. If the steps are `h` metre high and `b` mere wide, the ball will just hit the edge of `n th` step. Find the value of `n`.

Explanation

By using equation of trajectory `y = (g x^2)/(2 u^2)` for given condition,
`n h = (g(n b)^2)/(2 u^2)`
or `n = (2 h u^2)/(g b^2)`.
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