A mule is a cross between a donkey and a horse. Therefore, a mule will have some donkey characteristics such as large ears, a head just a bit too large for its body, a skimpie â¦ r tail, some still have the cross on their backs from the donkey, and they often have small looking feet.
Density of air. The density of air, Ï (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere, and is a useful value in aeronautics and other sciences. Air density decreases with increasing altitude, as does air pressure. It also changes with variances in temperature or humidity.
Population densities- the frequency with which something occurs in space is density. Arithmetic density: The total number of people divided by the total land area. This is what most people think of as density; how many people per area of land. Physiological density: The number of people per unit of area of arable land, which is land suitable for agriculture. This is important because it relates to how much land is being used by how many people. *Agricultural density: the number of farmers per unit of area of farmland.