Question

A small coin is kept at the rim of a horizontal circular disc which is set into rotation about vertical axis passing through its centre. If radius of the disc is 5 cm and μ_s = 0.25, then the angular speed at which the coin will just slip is 

(A) 5 rad/s 

(B) 7 rad/s 

(C) 10 rad/s 

(D) 4.9 rad/s

Answer 1

Answer is (B) 7 rad/s

Using, μ_smg ≤ mrω²

μ_sg = rω² (For minimum angular speed)