Q.

Two small balls with masses m and 2m are attached to both ends of a rigid rod of length d and negligible mass. If angular momentum of this system is L about an axis (A) passing through its centre of mass and perpendicular to the rod then angular velocity of the system about A is:            [2026]

1 2Lmd2  
2 32Lmd2  
3 43Lmd2  
4 2L5md2  

Ans.

(2)

L=Iω  and  ω=LI

ω=Lm(2d3)2+2m(d3)2=L49md2+29md2=L6md29

ω=3L2md2