A) \[16.5\,km{{h}^{-1}}\]
B) \[11.2\,km{{h}^{-1}}\]
C) \[10\,km{{h}^{-1}}\]
D) \[8.8\,km{{h}^{-1}}\]
Correct Answer: A
Solution :
Using law of conservation of energy \[\frac{1}{2}m{{v}^{2}}=\frac{1}{2}m[{{(20)}^{2}}-v_{e}^{2}]\] Here escape velocity\[{{v}_{e}}=8\sqrt{2}km{{h}^{-1}}\] \[\therefore \] \[{{v}^{2}}={{(20)}^{2}}-{{(8\sqrt{2})}^{2}}\] \[=400-128\] \[=272\] So, \[v=16.5km{{h}^{-1}}\]
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