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.
More accurately, nitrogen, which is a constituent gas of air, is less dense than air, not lighter.   The density of air at standard temperature and pressure is 1.292 kg/m3. The density of nitrogen is 1.251 kg/m3. Shelly McFarland Faleska.