A stone falls freely from rest from aheight `h` and it travels a distance `9h//25` in the last second. The value of `h` is

Options

A. 100 m
B. 122.5 m
C. 145 m
D. 167.5 m

Answer

B

Explanation

Let `h` distance is covered in `n` sec.
`rArr h = (1)/(2) gn^2`…(i)
Distance covered in `n^(th) sec = (1)/(2) g(2n - 1)`
`rArr (9h)/(25) = (g)/(2) (2n - 1)` …(ii)
From (i) and (ii), `h = 122.5 m`.