A) \[~10\,m{{s}^{-1}}\]
B) \[~14\,m{{s}^{-1}}\]
C) \[~20\,m{{s}^{-1}}\]
D) \[~28\,m{{s}^{-1}}\]
Correct Answer: C
Solution :
Let ball rebound with speed v, so \[v=\sqrt{2gh}=\sqrt{2\times 10\times 20}=20\,m/s\] Energy just after rebound \[E=\frac{1}{2}\times m\times {{v}^{2}}=200\,m\] 50% energy loses in collision means just before collision energy is 400 m By using energy conservation, \[\frac{1}{2}mv_{0}^{2}+mgh=400\,m\] \[\Rightarrow \]\[\frac{1}{2}mv_{0}^{2}+m\times 10\times 20=400\Rightarrow {{v}_{0}}=20\,m/s\]You need to login to perform this action.
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