Why are african pygmies diminutive.Is it is due to lack of GH, thyroxine or absence of thyroxine receptors on their cell surface ?

Metals get attacked by substances around it such as moisture, acids, etc. Metal is said to 'corrode' due to this attack and the process is called corrosion. Many metals like iron, copper, silver, etc. get corroded. When iron is exposed to moist air, it undergoes corrosion and a reddish brown coloured solid layer is formed on its surface. Corrosion of iron, which is known as rusting, is a serious problem as enormous amount of money is spent every year to replace damaged iron. Similarly, copper reacts with moisture and. CO_(2) in air to form a green coloured coating of basic copper carbonate on its surface. Silver acquires a black colour when exposed to air containing H_(2)S due to the formation of silver sulphide on its surface. Based on the above paragraph, answer the following question. Why do we apply paint on iron articles?

Let 'g_h' and 'g_d' be the acceleration due to gravity at height 'h' the above the earth's surface and at depth 'd' below the earth's surface respectively. If g_h= g_d then the relation between 'h' and 'd' is

What is the variation in acceleration due to gravity with altitude? OR Derive an expression for the gravitational acceleration at an altitude h above the earth. OR Show that the gravitional acceleration at a height h above the surface of the earth is (in usual notations) g_h = g (frac(R)(R + h)^2)

Show that acceleration due to gravity at height h above the Earth’s surface is g_h = g ((R )/(R+h))^2