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, \[v=16.5\,km\,{{h}^{-1}}\]
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