Agate is good protective energy stone, especially for children, and is very calming and soothing. It also can help strengthen the body's connection to the earth.
The friction factor, f, is a dimensionless factor that depends primarily on the velocity u, diameter D, density Ï, and viscosity Î·. It is also a function of wall roughness which depends on the size Îµ, spacing Îµ' and shape of the roughness elements characterized by Îµ''.
Friction is a force caused by the contact of one surface on another. It results in the resistance of an object moving over a surface. For example, it's easier to move your hand over fine sandpaper than rough sandpaper because less friction is produced by the surface of the fine sandpaper.