大氣壓的真正完成原因(最好是從書上或老師的話中得知)

Atmospheric pressure is result of random motion (thermal motion) of air molecules. The molecules constantly bombard a surface or an area, the change of momenta of the molecules during bombardment produces air pressure.

Q:1.大氣壓是因為大氣有重量而形成的.

A: Air pressure exerts in all directions. It is NOT merely due to the weight of the air in the atmosphere which only acts in a single downward direction. (this misleading concept may be due to some physics textbooks use an anaolgy of solid weight to introduce the concept of pressure and then extend it to cover fluid pressure.)


2.大氣壓是因為大氣對其化物質碰撞而形成的。

A: Yes, this is true. Air molecules move random;y in ALL direction because of their thermal energy. Thus pressure exerts in ALL directions with the same magnitude at a certain point in the atmosphere.

The reduction of air pressure as one goes up to higher altitudes is because of the decrease of temperature, thus reducing thermal energy of the molecules, which in turn leads to lower average momenta of the molecules. The force arsing from bombardment of air molecules (pressure) thus decreases.

I am giving you some hints, it is about water pressure, if you have a clear view of it, it is the same as the atmosphere prssure.

When you are in deep water, you will feel the water pressure comes from all direction. The way that you will not be crush by the water pressure is 1) Your shell(s) is (are) VERY VERY HARD, or 2) The pressure inside your body is the same as outside.

The water pressure is depends on only the depth of the water, if you use a narrow tube but very very high, you can make a large pressure with very little amount of water.

Some supplyment

If you a in a place with no gravity, there will be still air pressure, as you see in TV, there is air pressure inside spaceship, almost 1 atm. By thermophysics, there is n equation PV=nRT, where P is pressure, V is the volume of the fluid, n is the no. of molecules, R is the constant (I forget the name), and T is temperature in Kevin scale.