Consider the situation shown in figure (6-Q1). The wall is smooth but the surfaces of A and B in contact are rough. The friction on B due to A in equilibrium


As it is mentioned in the question that the wall is smooth, then there will be no friction between the blocks and the wall surface. The weight of the blocks will be in downward direction and no other force is present to counter the downward force. Hence, the system can never remain in equilibrium.

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