A) Reach the ground in 4 second
B) Begin to move down after being released
C) Have a displacement of 50 m
D) Cover a distance of 40 m in reaching the ground
Correct Answer: A
Solution :
When the stone is released from the balloon. Its height \[h=\frac{1}{2}a{{t}^{2}}=\frac{1}{2}\times 1.25\times {{(8)}^{2}}=40\ m\] and velocity \[v=at=1.25\times 8=10\ m/s\] Time taken by the stone to reach the ground \[t=\frac{v}{g}\left[ 1+\sqrt{1+\frac{2gh}{{{v}^{2}}}} \right]=\frac{10}{10}\left[ 1+\sqrt{1+\frac{2\times 10\times 40}{{{(10)}^{2}}}} \right]\]=4 sec
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