Question

A stone has fallen from the top of the tower. It runs 24.5m in the last second of its journey. What is the hight of the tower

Answer 1

Let the stone reaches the ground in n seconds

As per question, The distace travelled by the stone in its last second(i.e nth second) = 24.5m

Applying the formula, S(nth) = u + a/2(2n -1)

we have, 24.5 = 0 + 10/2(2n-1) (here a = acceleration due to gravity = 10m/s²)

2n - 1 = 24.5/5

2n - 1 = 9

n = 5

Now applying the formula, S = ut + 1/2 at²

we have, h = 0t + 1/2×10×(5)² = 125

So, Height of the tower is 125m