A uniform rod has mass m and length l. One end of the rod lies on rough surface at an angle of 60 degrees. The other end is connected to a vertical string. Find the friction force after the string is cut, assuming that there is no slipping between rod and surface.

Question

anonymous · Answer

a diagram might help.   Also I think we need more information.

anonymous · Answer

attachment

anonymous · Answer

That helps alot. thanks

anonymous · Answer

Here is a diagram showing relevant forces acting
|dw:1415893857773:dw|

The weight is 16/sqrt(3) newtons.  small f is the component of the weight transfered down the rod to the horizontal surface.  Large F is the frictional force keeping the rod from slipping. Since the rod does not move  F must equal the horizontal component of  f.  Can you take it from here?

anonymous · Answer

Yeah thanks!  But can't it be solved using rotational dynamics?

anonymous · Answer

No. The frictional force is acting at the point of  rotations so it has no effect on the rotation.  It cannot be related to anything causing the rotation.

anonymous · Answer

I really appreciate your help. Thanks for clearing my doubt!