[" A.In force by the rod on one of the bioks in surface."],[" 20.A block of mass "M" is kept on a rough horizontal surface."],[" The coefficient of static friction between the block and "],[" the surface is "mu" .The block is to be pulled to slide the "],[" a force to it.What minimum force is needed to slide the "],[" block? In which direction should the board and the floor "]