A block of weight 40 N lies on a rough board inclined at an angle of 10∘ 10^\circ\,10∘ to the horizontal. A horizontal force of 20 N acts on the block and the block is in equilibrium on the point of slipping up the board.
Find the coefficient of friction between the block and the board.
The 20 N force is removed. Determine whether or not the block moves.
