eloquent logic - dynamics

Legend

F_net	=	net force
m	=	mass
a	=	acceleration
F_g	=	force of gravity
F_N	=	normal force

重量

當研究任何地球上的物體時，一定要注意到地吸引力 (F_g)‧

F_g = mg

where g = acceleration caused by gravity's pull. It equals approximately 9.81 m/s² for objects near the earth. We will later on derive the value of g in the gravitation section.

任何物體的質量在宇宙任何一個角落都是一樣的‧但是在它的重量卻依著地點而改變‧在地球表面上加速度是9.8 m/s²‧

地吸引力向下作用，同時地球表面向上頂著，此反作用力是法向反作用力(F_N)‧如此我們可以平衡的站定，而不被地吸引力拉下地球中心‧

由於引力 (gravitational pull) 或重力 (gravity) 作用，所以這作用在該物體上的力就定義為物體的重量 W(weight)。因此:

W = mg	g	= 重力加速度
		= 9.81 ms^-2

Free-body diagram showing two forces acting on a standing person, the force due to gravity, and the normal force which is the reaction on the floor

Vector Dynamics

Friction