The load bar of negligible weight is screwed in place between the walls of the truck bed in order to keep loads from shifting. Determine the torsional moment M that must be applied to the center of the bar so that it produces a compression in the bar of 80 lb. The square-threaded screw at A has a lead of 0.2 in. and a radius of 0.5 in., and the coefficient of static friction between the bar and the screw is μ_s = 0.3. Also, what amount of horizontal force F must be applied to the center of the bar to pull it out? The coefficient of static friction between the walls of the truck and the end pads is μ_s = 0.7.

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A M B