A fraction of a degree of movement in the angle of contact
with a boot can make all the difference between the ball flying into the top corner of the net or hitting the frame of the goal and bouncing out.
By applying a droplet of the flux material, the angle of contact
reveals the nature of the surface energy (FIGURE 5).
Angle of contact
can also be calculated by measuring height and base length of spherical drop.
This model, however, doesn't capture the full three-dimensional nature of the forces acting between grains, in which the downward force of gravity is translated into the sum of forces acting in different directions between the grains, depending on their angle of contact