5. Place four small balls with a radius of 1 on the table in two layers: three on the bottom layer, one on the top layer, each touching the others. Find the height from the highest point of the top ball to the table.
As shown in the figure, $A, B, C, D$ are the centers of four small balls, then $A B C D$ is a regular tetrahedron with a side length of 2, its height $D O=\frac{2 \sqrt{6}}{3}$, so the height from the highest point of the upper ball to the table is $M N=\frac{2 \sqrt{6}}{3}+2$.