two cylindrical hollow drums of radii R and 2 R, and of a common height h , are rotating with angular velocities `omega` (anti- clockwise ) and `omega` (clockwise ) , respectively , their axes , fixed are parallel and in a horizontal plane separated by by 3R + `delta` , they are now brought in contact `(delta to0)`
(A) show frictional forces just after contact .
(B) identify forces and torque external to the system just after contact ,
(c) what would be the ratio of final of final angular velocities when friction ceases ?

Explanation

Consider the situation shown below we have shown the frictional forces .

(b) `F'= F=F` where F and F are external forces through support
`implies F_("net")=0 ("one each cylinder")`
External torque `=Fxx3R` (anti- clockwise )

( c) Let `omega _(1)` and `omega_(2)` be final angular velocites of samaller and bigger drum respectively (anti - clokwise and clockwise Respectivelty)
Hence , `Romega_(2)implies(omega_(1))/(omega_(2))=2`
Note :- We should be very careful while indicating direction of frictional forces.