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A child stands, hands at the side, on a turntable. The kinetic energy of system is K. The child now raises his arms, and the moment of inertia of system becomes twice. Then the kinetic energy of system will be …………

Answer» <html><body><p>`<a href="https://interviewquestions.tuteehub.com/tag/2k-300402" style="font-weight:bold;" target="_blank" title="Click to know more about 2K">2K</a>`<br/>`(K)/(2)`<br/>`(K)/(<a href="https://interviewquestions.tuteehub.com/tag/4-311707" style="font-weight:bold;" target="_blank" title="Click to know more about 4">4</a>)`<br/>`4K`</p>Solution :No <a href="https://interviewquestions.tuteehub.com/tag/external-981194" style="font-weight:bold;" target="_blank" title="Click to know more about EXTERNAL">EXTERNAL</a> <a href="https://interviewquestions.tuteehub.com/tag/force-22342" style="font-weight:bold;" target="_blank" title="Click to know more about FORCE">FORCE</a> is acting so angular momentum is constant <br/> `therefore I_(<a href="https://interviewquestions.tuteehub.com/tag/1-256655" style="font-weight:bold;" target="_blank" title="Click to know more about 1">1</a>)omega_(1)=I_(2)omega_(2)` <br/> `therefore omega_(2)=(I_(1)omega_(1))/(I_(2))=(omega_(1))/(2)[because I_(2)=2I_(1)]` <br/> Now rotational kinetic energy <br/> `therefore K_(1)=(1)/(2)I_(1)omega_(1)^(2)` and <br/> `therefore K_(2)=(1)/(2)I_(2)omega_(2)^(2)` <br/> `=(1)/(2)(2I_(1))((omega_(1))/(2))^(2)` <br/> `=(1)/(2)(I_(1)omega_(1)^(2))/(2)` <br/> `=(K)/(2)`</body></html>


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