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

Let ‘n’ be the last second of its fall then sn=gn−12..........(i)  The distance travelled by a freely falling body in the last sec is   But h=12gt2=12g(1)2=g2………..(i)∴ from (i) 7h=gn−12⇒7g2=g2(2n−1)⇒2n−1=7⇒n=4s∴ The time taken to reach the ground is  4s