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.
Less air density means less lift. The air density at sea level is 1.225 kg per cubic meter (Source). However, as you go higher above sea level, air density begins to decrease. This is why people sometimes have difficulty breathing at higher altitudes in mountainous regions.