The air envelope is thicker near the earth's surface and we go higher the density and availability of air gradually decreases, Why?

About 71% of earth's surface is covered with water,then why do we face scarcity of water?

An air bubble of radius r in water is at a depth h below the water surface at some instant if P is atmospheric pressure and d & T are the density and surface tension of water, what is the pressure inside the bubble ?

a. The top of the atmosphere is at about 400 kV with respectto the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about 100 Vm^(-1). Why then do we not get a electric shock as we step out of our house into the openy (Assume the house to be a steel cage so there is no field inside!) b. A man fixes outside his house one evening a two metre high insulating slab carrying on its top a large aluminium sheet of area 1m^(2) . Will he get an electric shock if he touches the metal sheet next morning? c. The discharging current in the atmosphere due to the small conductivity of air is known to be 1800A on an average over the globe. Why then does the atmosphere not discharge itself completely in due course and become electrically neutral? In other words, what keeps the atmosphere charged? d. What are the forms of energy into which the electrical energy of the atmosphere is dissipated during a lightning? (Hint: The earth has an electric field of about 100 Vm^(-1) at its surface in the downward direction, corresponding to a surface charge density =-10^(-9) Cm^(-2) ?.

The force of buoyancy exerted by the atmosphere on a balloon is B in the upward direction and remains constant. The force of air resistance on the balloon acts opposite to the direction of velocity and is proportional to it. The balloon carries a mass M and is found to fall down near the earth's surface with a constant velocity v. How uch mass hsould be removed from teh balloon so that it may rise with a constant velocity v?

Explain why one can jump higher on the surface of the Moon than that on the Earth.

Two charged conducting spheres of radii a and b are connected to each other by a wire. What is the ratio of electric fields at the surfaces of the two spheres? Use the result obtained to explain why charge density on the sharp and pointed ends of a conductor is higher than on its flatter portions.

Suppose the density of air at Madras is rho_0 and atmosphere pressure is P_0. If we go up the density and the pressure both decreae. Suppose we wish to calculate the pressure at a height 10 km above Madras. Ilf we use the equation P_0-P=rho_0gz will we get a pressure more than the actual or less than the actual? Neglect the variation in g. Does your answr change if you also consider the variation in g?