Q A solid cylinder of mass m and radius r is rolling on a rough inclined plane of inclination θ. The coefficient of friction between the cylinder and incline is m. Then

(A) frictional force is always mmg cos θ

(B) friction is a dissipative force

(C) by decreasing θ, frictional force decreases

(D) friction opposes translation and supports rotation

Dear Mainak

N = mgcosx

maximum frictional force  f= μN =μmgcosx

 this friction force will not always act .it is the maximum possible frictional force.

 a= (mgsinx -f)/m

for pure rollinr  α =a/r

and torque f.r  = mr²/2 α

                 f  =ma/2

                    =m/2 (mgsinx -f)/m

                f = mg/3 sinx

by decresing x frictional force decreses

 so  d option is correct

Please feel free to post as many doubts on our discussion forum as you can.
If you find any question Difficult to understand - post it here and we will get you
the answer and detailed  solution very  quickly.

 We are all IITians and here to help you in your IIT JEE preparation.

All the best.
 
Regards,
Askiitians Experts
Badiuddin