The uniform rectangular block is released from rest with θ essentially zero and pivots i...

The uniform rectangular block is released from rest with θ essentially zero and pivots in the vertical plane about the center A of its lower face on the fixed corner. (a) If the block is observed to slip when θ = 30°, find the coefficient of static friction between the block and the corner. (b) If the bottom face of the block is notched so that it cannot slip, find the angle θ at which contact between the block and the corner ceases.