A) \[5\,\,m/s\]
B) \[10\,\,m/s\]
C) \[15\,\,m/s\]
D) \[20\,\,m/s\]
Correct Answer: A
Solution :
Key Idea: Maximum kinetic energy of swing should be equal to difference in potential energies to conserve energy. From energy conservation \[\frac{1}{2}mv_{\max }^{2}=mg({{H}_{2}}-{{H}_{1}})\] Here, \[{{H}_{1}}=\]maximum height of swing from earth's surface \[=0.75\,\,m\] \[{{H}_{2}}=\]maximum height of swing from earth's surface \[=2\,\,m\] or\[{{v}_{\max }}=\sqrt{2\times 10\times 1.25}=\sqrt{25}=5\,\,m/s\]
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