Question

A balloon is rising vertically up with a velocity of $29$ $m{s}^{-1}$. A stone is dropped from it and it reaches the ground in $10$s. The height of the balloon when the stone was dropped from it is: $(g=9.8m{s}^{-1})$.

• A. $400$m
• B. $150$m
• C. $100$m
• D. $200$m

Answer 1

The correct option is D $200$m

For a stone which is thrown downwards from a balloon rising upwards, the equation of motion is
$h=-ut+\frac{1}{2}g{t}^2$
$=-29\times 10+\frac{1}{2}\times 9.8\times (10{)}^2$
$=-290+490$
$=200$m.