Question

A body thrown vertically up with a finite speed is caught back after $4\text{sec}$. The speed of the body with which it is thrown up is
(Take $g=10{\text{m/s}}^2$)

• A. $10\text{m/sec}$
• B. $20\text{m/sec}$
• C. $30\text{m/sec}$
• D. $40\text{m/sec}$

Answer 1

The correct option is B $20\text{m/sec}$

Given, time of flight of the body $=4\text{sec}$
We know that, time of flight is given as
$T=\frac{2u}{g}\Rightarrow u=\frac{gT}{2}=\frac{10\times 4}{2}=20\text{m/s}$