A bead is constrained to move on rod in gravity free space as shown in figure. The rod is rotating with angular velocity ω and angular acceleration α about its end. If µ is coefficient of friction. Mark the correct option. (Rod rotates in the plane of paper)

Question

G1 Physics · Accepted Answer

If the bead stays fixed on the rod, friction supplies mω²r and the normal supplies mαr. Static friction requires mω²r≤µmαr, i.e. µ≥ω²/α; equality is limiting static friction. Hence A.