A long horizontal rod has a bead which can slide along its length, and initially placed at a distance \[L\] from one end \[A\] of the rod. The rod is set in angular motion about \[A\] with constant angular acceleration\[\alpha \]. If the coefficient of friction between the rod and the bead is \[\mu \], and gravity is neglected, then the time after which the bead starts slipping is

• A. \[\sqrt{\frac{\mu }{\alpha }}\]               
• B. \[\frac{\mu }{\sqrt{\alpha }}\]
• C. \[\frac{1}{\sqrt{\mu \alpha }}\] 
• D. Infinitesimal