A) \[4\,\,m\]
B) \[2\,\,m\]
C) \[1\,\,m\]
D) \[0.4\,\,m\]
Correct Answer: D
Solution :
Key Idea: At a given height the half of the kinetic energy of the body is equal to its potential energy. Initial kinetic energy of the body \[=\frac{1}{2}m{{v}^{2}}\] \[=\frac{1}{2}m{{(4)}^{2}}=8\,\,m\] Let at height\[h\], the kinetic energy reduces to half, \[ie,\] it becomes\[4\,\,m\]. It is also equal to potential energy. Hence,\[mgh=4\,\,m\]or \[h=\frac{4}{g}=\frac{4}{10}=0.4\,\,m\]
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