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 the stone to reach the ground for die remaining distance is

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

Answer 1

The Correct Option is C

From, \(s=ut+\frac{1}{2}at^{2}\) Distance covered in \(5s\) \(s=0+\frac{1}{2}\times 10\times 5^{2}=125\,m\) Distance covered in \(3\,s\) \(s=0+\frac{1}{2}\times 10\times 3^{2}=45\,m\) Distance

 to be covered \(125-45=80\,m\) From, \(s=ut+\frac{1}{2}at^{2}\) \(80=0+\frac{1}{2}\times 10\,t^{2}\) \(t^{2}=\frac{80}{5}=16\) \(t=4\,s\)