A) 14.7 m
B) 19.6 m
C) 9.8 m
D) 24.5 m
Correct Answer: A
Solution :
Height travelled by ball (with balloon) in 2 sec \[{{h}_{1}}=\frac{1}{2}a\ {{t}^{2}}=\frac{1}{2}\times 4.9\times {{2}^{2}}=9.8\ m\] Velocity of the balloon after 2 sec \[v=a\ t=4.9\times 2=9.8\ m/s\] Now if the ball is released from the balloon then it acquire same velocity in upward direction. Let it move up to maximum height \[{{h}_{2}}\] \[{{v}^{2}}={{u}^{2}}-2g{{h}_{2}}\] Þ \[0={{(9.8)}^{2}}-2\times (9.8)\times {{h}_{2}}\]\[\therefore \]\[{{h}_{2}}\]=4.9m Greatest height above the ground reached by the ball \[={{h}_{1}}+{{h}_{2}}=9.8+4.9=14.7\ m\]
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