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A rod PQ of mass M and length L is hinge...

A rod `PQ` of mass `M` and length `L` is hinged at end `P`. The rod is kept horizontal by a masseless string tied to point `Q` as shown in Fig. When string is cut, the initial angular acceleration of the rod is :

Text Solution

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The correct Answer is:
B
If `I` is moment of inertia of the rod about the end `P and alpha` is initial angular acceleration of the rod,
then as is clear from Fig.
`tau = I alpha = Mg xx (L)/(2)`

But `I = (ML^(2))/(3) :. (ML^(2))/(3) alpha = Mg (L)/(2)`
`alpha = (3g)/(2L)`
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