Question

A stone falls from a balloon that is descending at a uniform rate of $12\text{m/s}$. The displacement of the stone from the point of release after $10\text{sec}$ is (take $g=9.8m/s^2$)

• A. $490\text{m}$
• B. $510\text{m}$
• C. $610\text{m}$
• D. $725\text{m}$

Answer 1

The correct option is C $610\text{m}$

Initial velocity of the stone $u=12\text{m/s}$
(taking downward direction as positive)

Using second equation of motion, after $t=10\text{s}$, displacement of the stone is given by

$s=ut+\frac{1}{2}g{t}^2$
$=12t+4.9t^2$
(taking $g=9.8{\text{m/s}}^2$)
$=120+4.9\times 100$
$=610\text{m}$