If the create has a mass of 90 kg and is 1.6 {\rm m} tall and 0.80 {\rm m} in depth and width, what is the minimum force needed to make the crate start tipping? (Assume the center of mass of the crate is at its center and static friction great enough to prevent slipping.)

It matters where the force is applied. If it is applied at a top edge, then

summing forces about the bottom corner

Force*1.6=mass*g*.4

solve for force in newtons.