Question

A stone is dropped from the 25th storey of a multistoried building and it reaches the ground in 5 s. In the first second, it passes through how many storeys of the building? (g = 10 $m{s}^{-2}$)

• A. 1
• B. 2
• C. 3
• D. none of these

Answer 1

The correct option is A 1

Let the height of each storey $=h$

$2^{nd}$ equation of motion from starting point to A-

$h_1=0+\frac{1}{2}g(1{)}^2\Rightarrow h_1=\frac{g}{2}$

$2^{nd}$ equation of motion from starting point to B-

$25h=0+\frac{1}{2}\times g\times \left(25\right)25h=\frac{25g}{2}\Rightarrow h=\frac{g}{2}$

$h=h_1$

In one second it passes one storey