反作用力，作用力和friction

a action force is always equal to it's reaction force in strenght...
but they are always in opposite direction,,,

second ,,,yes,,,
but the "加速" is too small as the mass of the earth is too large

一對"作用力"及"反作用力"有以下幾個特性:

1) 作用力及反作用力分別作用在不同的物體上
2) 作用力及反作用力的大小相同
3) 作用力及反作用力的方向相反

回答你的問題:
1) No. The magnitude of action and reaction force should be the same but in opposite direction.
2) The force we exerted on the earth and the force the earth exerted on us is a pair of action and reaction force. They are of the same magnitude but in opposite direction.

注意:
1) 你不用把earth surface 同earth center 分開來看, 事實上它們都是同一件物體earth。
2) 當你考慮一個力的時候一定要清楚知道這個力是由什麼東西作用在什麼東西上。
3) 你可以運用以下的句式去說明一個力:
a) The force A exerted on B
b) The force exerted on B by A
c) The force exerted by A on B
幾句都是說A給予B一個力, 當你要分析題目畫B的"自由物體圖(free-body diagram)"時, 你只用考慮The force exerted ON B, 而不用考慮the force exerted BY B.

A1.
By Newton's third law, action and reaction is the same in strength but in opposite direction.

A2.
We react on the earth surface is smaller than the gravity putting us towards the earth centre.

Gravitational force acts on us from the earth = gravitational force acts on the earth from us (action and reaction pairs)
= centripetal force acts on us + our weight

However, we react on the earth surface = our weight.