physics
posted by Anonymous .
What is the minimum downward force on the box in the figure that will keep it from slipping? The coefficients of static and kinetic friction between the box and the floor are 0.35 and 0.25, respectively.

The question is incomplete, probably the figure has not been described.
I can visualize a box on a horizontal floor, but I do not see how and why the box would slip without any external force.
Please provide a complete description of the figure. 
What is the minimum downward force on the box in the figure that will keep it from slipping? The coefficients of static and kinetic friction between the box and the floor are 0.40 and 0.30, respectively.