A uniform \( \operatorname{rod} A B \) of mass \( m \) and length \( 2 a \) is falling freely wi...

A uniform \( \operatorname{rod} A B \) of mass \( m \) and length \( 2 a \) is falling freely without rotation under gravity with \( A B \) horizontal. Suddenly
\( \mathrm{P} \) the end \( A \) is fixed when the speed of the rod is \( v \). The angular

W speed with which the rod begins to rotate is
(1) \( \frac{v}{2 a} \)
(2) \( \frac{4 v}{3 a} \)
(3) \( \frac{v}{3 a} \)
(4) \( \frac{3 v}{4 a} \)