Given,
Lac < Lcb
Also, Weight of rod of length L is W1
Let weight of part ac be Wac and of part cb be Wcb.
therefore,
Wac = W1 ( Lac / L )
and, Wcb = W1 ( Lcb / L)
clearly, Wac < Wcb (since, Lac < Lcb)
Therefore, rod will tend to move anticlockwise,
Thus friction at contact point of rod and ground will act in backward direction.