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dynamics2.gif (411 bytes)

Legend

Fnet

 = net force

m 

= mass

a 

= acceleration

Fg

 = force of gravity

FN

 = normal force

向量動力
在動力學，有很多外來的作用力•最後要找的是總力•而此總力是個向量•所以相反方向的力可以相減•

要找總力需要自由力體圖 (free-body diagrams) •畫出所有在一個物體上的作用力•

Example:

自由力體圖:
當棒球被丟時•

 Baseball's free body diagram taken while being thrown by pitcher
自由力體圖:
當棒球還在投手手上時•		 Baseball's free body diagram taken after it has been released from the pitcher
Example 2:
Image of boy pulling along a cart, the force is diagonal so we can break it into components The horizontal and vertical forces and how to find them
我們在有向運動學中知道向量可以分成水平和垂直兩方向•這男孩拉著拉車，他的力量可以分成水平方向Fcos30.0o 而垂直兩方向是Fsin30.0o•
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created by Will Kuo and Stan Watterson
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