Friction 係咪一定等於 Action

我想講你俾force落一樣野到，個reaction force 係act 落你隻手，唔係friction。friction 只係一個opposing force，因為佢係opposing force，所以你俾個force要大過佢=有net force。咁樣野就會move。

ps：action and reaction are equal in magnitude, opposite in direction, on different object (Aact on B, B react on A).

唔係

friction只係一個力 佢只會影響加速度

唔會直接改變你個速度

單純判斷一件物件是否移動

係無辦法得知friction係咪比較大

要知道friction 應該判斷加速度 而唔係速度

其次 跟據牛頓第三定律

作用力同反作用力係永遠相同但相反的

從你既例子中

地面作用響物件既friction既反作用力

係物件作用返響地面既力

而唔係物件既推動力

The "action" you refer to is actually the "applied force" in pulling the object to move. This "applied force" and friction is NOT an action-reaction pair. Hence their magnitudes are independent of each other, and may not be necessarily equal.

The "reaction" of the "applied force" acts on the agent that applies the force, e.g. you hand (that pulls the object). The "reaction" of friction acts on the surface on which the object is rested.

action and reaction 唔係永遠相等
but an action comes with reaction in pair
example:
F action>F friction when things move on surface

2010-04-08 19:13:34 補充：
I apologize that I am wrong