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A bal tied to a sting takes 4 s to compl...

A bal tied to a sting takes 4 s to complete revolution along a horizontal circle. If by pulling the cord, the radius of the circle is reduced to half of the previous value, then how much time the ball will take in one revolution.

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Formula: By conservation of angular momentum
`I_(1)omega_(1)=I_(2)omega_(2)`
or `mr^(2). (2pi)/(T_(1))=m(r/2)^(2) .(2pi)/(T_(2))`
Time taken by the ball,
`Tk_(2)=1/4 T_(1)`
`=1/4xx4=1s`
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