Graphite has a hexagonal crystal structure where a = b ≠ c and the angles α = β = 90°, γ = 120°. This structure contributes to its unique layered properties, which are characteristic of hexagonal systems. The other options do not satisfy these structural parameters.
A wooden block of mass M lies on a rough floor. Another wooden block of the same mass is hanging from the point O through strings as shown in the figure. To achieve equilibrium, the coefficient of static friction between the block on the floor and the floor itself is