A body dropped from the top of the tower covers a distance 7 h in the last second of its journey where h is the distance covered in the first second. How much time does it take to reach the ground ?

Using the formula v2 = u2 + 2 g h, we have0=u2−2gh or u2=2gh0=(2u)2−2gH or 4u2=2gH∴hH=14 or 4h=Hsn=12g(2n−1)or 7h=12g(2n−1)....(1)and h=12g(2−1) or h=g2...(2)From eqs. (1) and (2), we get7×g2=12g(2n−1)or 7=(2n-1) or n=4hence t = 4sec