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June 25, 2019, 09:59:46 pm

Author Topic: Deriving Ek  (Read 686 times)  Share 

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Mao

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Deriving Ek
« on: January 04, 2008, 09:22:51 am »
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I was just wondering the other day, many of the VCE physics formulas are derived from very simple equations, e.g. the 5 formulas dealing with constant acceleration and etc...

however no textbooks i've come across to have shown the workings to
obviously you do not need that for the course, but just out of curiosity, where is this formula derived from? if at all??

i tried substituting stuff to , but most of it ended nowhere...
this was what i got...



given that

therefore

given that

and i'm stuck....
:(


Thanks!!
« Last Edit: January 04, 2008, 09:25:06 am by Obsolete Chaos »
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Collin Li

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Re: Deriving Ek
« Reply #1 on: January 04, 2008, 09:31:50 am »
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http://en.wikipedia.org/wiki/Kinetic_energy#Derivation_and_definition

This is the correct way to do it. To fix your equation, you have to consider that Work is an input of energy, so the shows a change in velocity, proportional to the change in work. Kinetic energy sets a reference point: .

Ahmad

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Re: Deriving Ek
« Reply #2 on: January 04, 2008, 10:07:42 am »
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To perhaps most accurately define work done you'd need to use line integrals, however think about this:





(Since a = dv/dt = dv/dx * dx/dt = dv/dx * v)

(We don't worry about v=a, since we want total KE, we want the work done from rest!).
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Mao

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Re: Deriving Ek
« Reply #3 on: January 04, 2008, 01:03:08 pm »
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riiight, that make sense now! thanks guys...
=D

and i have no idea how line integral works.... someday... ;D
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