The post is made of Douglas fir and has a diameter
of 60 mm. If it is subjected to the load of 20 kN and the
soil provides a frictional resistance that is distributed
along its length and varies linearly from w = 0 at y = 0 to
w = 3 kN>m at y = 2 m, determine the force F at its bottom
needed for equilibrium. Also, what is the displacement of
the top of the post A with respect to its bottom B? Neglect
the weight of the post.