Question

A stone is dropped from a rising balloon at a height of 300 m above the ground and reaches the ground in 10 s. The velocity of the balloon when it was dropped is ?

Answer 1

$$\begin{gathered} \mathrm{Sign}\mathrm{convention}: \\ \mathrm{Up}:+\mathrm{ve}\mathrm{and}\mathrm{down}:-\mathrm{ve} \\ \mathrm{From}\mathrm{the}\mathrm{equations}\mathrm{of}\mathrm{motion}\mathrm{of}\mathrm{kinematics}, \\ \mathrm{s}=\mathrm{ut}+\frac{1}{2}{\mathrm{at}}^2 \\ -300=\mathrm{u}\left(10\right)-\frac{1}{2}\times 9.8\times {10}^2 \\ 10\mathrm{u}=490-300 \\ \mathrm{u}=19\mathrm{m}/\mathrm{s} \end{gathered}$$