Humans have two kidneys and each kidney is supplied with blood from the renal artery. The kidneys remove from the blood the nitrogenous wastes such as urea, as well as salts and excess water, and excrete them in the form of urine.This is done with the help of millions of nephrons present in the kidney.umans have two kidneys and each kidney is supplied with blood from the renal artery. The kidneys remove from the blood the nitrogenous wastes such as urea, as well as salts and excess water, and excrete them in the form of urine.
This is because the speed of sound waves depends upon the material through which they are travelling. Sound travels 15 times faster through the metal railway tracks than through air, giving the cowboy an early warning of the train's arrival. How much plainer could it be? I, personally, had never thought of it that way. I love this illustration.
Let's add a few words to them to clarify.  Nothing can travel faster than the speed of light in a vacuum.  . Light in a vacuum always travels at the same speed.  Those additional three words in a vacuum are very important. A vacuum is a region with no matter in it. So a vacuum would not contain any dust particles (unlike a vacuum cleaner, which is generally full of dust particles). Light traveling through anything other than a perfect vacuum will scatter off off whatever particles exist, as illustrated below. In vacuum the speed of light is c = 2.99792458 x 108 m/s.