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如能量是由運動 (motion)
引起，那麼我們可以稱這種能量為 "動能"•
公式:
KE = 1/2 mv2
如果一物體以 vi 的初始速移動，作用在物體上的功
(當末速是 vf )將會是 :
Wnet =  KE
= 1/2 mvf2 - 1/2 mvi2
如何得到 KE = 1/2 mv2 ?
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W =
Fd |
and |
| F = ma |
so, |
| W= mad |
And from what
we derived in vector
kinematics section: |
| Vf2 = Vi2
+ 2ad |
Hence, |
| ad = 1/2 vf2
- 1/2 vi2 |
And
multiplying both sides by m yields: |
| Wnet = 1/2 mvf2
- 1/2 mvi2 |
We
define the kinetic energy of any object of mass m traveling at speed v as: |
| KE = 1/2 mv2
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當棒球被丟出時，它的動能改變因為速度加快• |
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