物理摩擦力--看得懂英文的进!A 41 kg box rests on a level surface.The coef

物理摩擦力--看得懂英文的进!
A 41 kg box rests on a level surface.The coefficient of static friction,μS = 1.1 and the coefficient of kinetic friction,μK = 0.7 .
求：F(gravity) on box from surface
FNormal on box from Earth
Ffriction on box from surface
请大大解释coefficient of static friction 和 coefficient of kinetic friction 到底是什么意思(那个东西没有动为什么会有kinetic friction),然后Fnormal,Fgravity 和 Ffriction 的意思.
最后..请不要上网给我那些单字的长篇资料,我是查过看不懂以后才来的!