機械能和內能的分別

I think you have mixed up the two situations.

In the statemnt: 總機械能=動能+勢能
here, the total mechanical energy (總機械能) refers, marcoscopicaly, to the sum of potential (勢能) and kinetic (動能) energies of an object. It is ususally observed as the motion or the position of the object.

However, in the statement: 內能=物體中所有粒子的動能與勢能的總和
here, the potential and kinetic energies refer to the molecular energy, i.e. energy possessed by molecules. Such energy is rarely referred to as "mechnaical energy". Instead, because this energy is demonstrated macroscopically as the "heat content" of an object (or the degree of coldness or hotness), it is thus more commonly called "internal energy"(內能).

兩個能量係唔同既,

總機械能=動能+勢能

呢度講既動能同勢能係指一件物件既, 舉個例子, 過山車由高處衝落黎, 位於高處既時候佢就有勢能, 衝落黎既時候就係動能, 成個過程就係由勢能轉成動能.

內能=物體中所有粒子的動能與勢能的總和

內能所講既就微觀一d, 你都知物質係由粒子組成, 粒子係會有振動, 呢個就係粒子既動能, 而粒子之間係有引力既, 呢個就係勢能, 舉個例, 煲水, 水本來就由粒子組成, 遇熱既時候粒子就會振動得更激烈, 當振動到可以擺脫粒子間既引力, 粒子就會飛出水面, 呢個就係蒸發, 所以呢個過程都係能量轉換既一種.

動能顧名思義就係移動/振動既時候既能量
勢能可以理解係引力(包括地心吸力)所給予既能量
總機械能同內能既分別係, 一個係睇成件物件, 而另一個係睇物件入面既粒子, 簡單d 就係宏觀同微觀既分別.

如果你問過山車有冇內能, 係有既, 不過係過山車飛馳既過程入面唔牽涉內能, 即係內能唔會有變, 咩情況有變呢, 就係當件物件既形狀、形態、溫度改變...等等既時候.

總機械能=動能+勢能, 但係能量唔只動能及勢能, 所以總機械能唔等於總能量.

<<如果上述解釋有錯, 請各位高人更正>>

-____-
我諗我明你意思掛-.-
thz``

2011-04-08 22:18:42 補充：
哈哈 NICE 吾該哂你阿
我ENG吾系甘好
原本明D吾明D
E+你講一講解我明哂! THZ!!