更新1:
where s is displacement
Explain an equation
2008-08-23 7:58 pm
Please explain why v2=u2 + 2as where v is final and u is initial velocity.
回答 (2)
2008-08-23 9:08 pm
✔ 最佳答案
The answer is as follows:圖片參考：http://i277.photobucket.com/albums/kk75/uncle_michael/080822_phy_1.jpg?t=1219468074
2008-08-24 7:20 am
definition of acceleration:
a = (v-u) / t ......................................(1)
definition of velocity:
V = s / t ...........................................(2)
definition of average velocity:
V = (v + u) / 2 ....................................(3)
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Combine (2) & (3),
(v + u) /2 = s /t
2 / (v + u) = t /s
t = 2s / (v + u) .....................................(4)
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Put (4) into (1),
a = (v-u) / t
a = (v-u) / [2s / (v + u)]
a = [(v-u)(v + u)] /2s
2as = (v-u)(v + u)
2as = v^2 - u^2
v^2 = u^2 + 2as .................................(result)
a = (v-u) / t ......................................(1)
definition of velocity:
V = s / t ...........................................(2)
definition of average velocity:
V = (v + u) / 2 ....................................(3)
_______________________________________
Combine (2) & (3),
(v + u) /2 = s /t
2 / (v + u) = t /s
t = 2s / (v + u) .....................................(4)
_______________________________________
Put (4) into (1),
a = (v-u) / t
a = (v-u) / [2s / (v + u)]
a = [(v-u)(v + u)] /2s
2as = (v-u)(v + u)
2as = v^2 - u^2
v^2 = u^2 + 2as .................................(result)
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