A thin rod MN , free to rotate in the vertical plane about the fixed end N , is held horizontal. When the end M is released the speed of this end, when the rod makes an angle $\alpha$ with the horizontal, will be proportional to:\\
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(1) $\sqrt { \cos \alpha }$\\
(2) $\cos \alpha$\\
(3) $\sin \alpha$\\
(4) $\sqrt { \sin \alpha }$