The caster wheel is subjected to the two couples. Determine the forces F that the bearings exert on the shaft so that the resultant couple moment on the caster is zero.
Let us write a moment equation assuming clockwise rotation is positive.
\circlearrowright^+ \sum M_A=0;
(Remember that our resultant couple moment on the caster should be zero, so our net moment is 0. Also, note that we did not convert mm to m as this was not necessary.)
Where you not suppose to convert mm to m?
It is not necessary.