When the 100-lb block is at h = 3 ft above the cylindrical post and spring assembly, it has a speed of v = 20 ft/s. If the post is made of 2014-T6 aluminum and the spring has the stiffness of k = 250 kip/in., determine the required minimum diameter d of the post to the nearest 1/8 in. so that it will not yield when it is struck by the block.
