A block A has been placed symmetrically over two identical blocks B and C. All the three blocks have equal mass, M each, and the horizontal surface on which B and C are placed is smooth. The coefficient of friction between A and either of B and C is `mu`. The block A exerts equal pressure on B and C. A horizontal force F is applied to the block B.

(a) Find maximum value of F so that A does not slip on B or C and the three blocks move together.
(b) If F is increased beyond the maximum found in (a) where will we see slipping first- at contact of A and B or at the contact of A and C.
(c) If F is kept half the maximum found in (a), calculate the ratio of friction force between A and B to that between A and C. Does this ratio change if F is decreased further?

Answer

`F_("max") = (3)/(4) mu Mg`
(b) Between A and B
(c) 2 , No