Question
A stone is dropped from a rising balloon at a height of $$76\,m$$ above the ground and reaches the ground in $$6s.$$ What was the velocity of the balloon when the stone was dropped? Take $$g = 10\,m/{s^2}.$$
A.
$$\left( {\frac{{52}}{3}} \right)\,m/s\,{\text{upward}}$$
B.
$$\left( {\frac{{52}}{3}} \right)\,m/s\,{\text{downward}}$$
C.
$$3\,m/s$$
D.
$$9.8\,m/s$$
Answer :
$$\left( {\frac{{52}}{3}} \right)\,m/s\,{\text{upward}}$$
Solution :
$$\eqalign{
& S = ut + \frac{1}{2}a{t^2} \cr
& - 76 = 4 \times 6 - \frac{1}{2} \times 10 \times {\left( 6 \right)^2} \Rightarrow u = \frac{{52}}{3}m/s \cr} $$