Question

A stone is dropped from a certain height which can reach the ground in $5$ s. If the stone is stopped after $3$ s of its fall and then allowed to fall again, then the time taken by stone to reach the ground for the remaining distance

• A. $2$ s
• B. $3$ s
• C. $4$ s
• D. None of these

Answer 1

The correct option is C $4$ s

From Case 1:
$S=ut+\frac{1}{2}g{t}^2$
$\Rightarrow S=\frac{25g}{2}$
From Case 2:
$S_1=ut+\frac{1}{2}g{t}^2=\frac{9g}{2}$
Now, $S_2=ut+\frac{1}{2}g{t}^2=\frac{g{t}^2}{2}$
As, $S=S_1+S_2$
$\Rightarrow \frac{25g}{2}=\frac{9g}{2}+\frac{g{t}^2}{2}$
$\Rightarrow t=4$ sec