Question

Figure shows two blocks $A$ and $B$ pushed against the wall with the force $F$ The wall is smooth but the surfaces in contact of $A$ and $B$ are rough Which of the following is true for the system of blocks to be at rest against wall?

• A. $F$ should be equal to weight of $A$ and $B$
• B. $F$ should be less than weight of $A$ and $B$
• C. $F$ should be more than weight of $A$ and $B$
• D. System cannot be in equilibrium (at rest)

Answer 1

Answer: (D)

For system A and B together there is no upward force to balance the weigh $(m_A+m_B)g$ So, system can never be in equilibrium