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392 posts

Ultimate Geek
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Topic # 229131 8-Feb-2018 21:30
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So any of you good at physics out there.

 

My 16 year old has asked me for help with his homework which is WAY over my head :)

 

 

 

So this is is it.....can you explain as well so we can both understand

 

 

 

Ep=1/2 Kx2 .......the two should be above the x as in squared

 

 

 

Use the equation to find K were Ep = 398J x=0.045m

 

 

 

Thanks


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29 posts

Geek
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  Reply # 1953896 8-Feb-2018 21:42
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393086.41975308646

 

Maybe..

 

http://calculator.tutorvista.com/physics/545/elastic-potential-energy-calculator.html

 

DFP




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Ultimate Geek
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  Reply # 1953897 8-Feb-2018 21:44
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I need to know how you work it out though ?




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Ultimate Geek
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  Reply # 1953899 8-Feb-2018 21:48
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I am more looking for how to re-arrange the equation and show the working as opposed to an internet resouce that just shows you the answer ....sorry


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Uber Geek
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  Reply # 1953901 8-Feb-2018 21:50
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It's just algebraic manipulation / re-arrangement of formulae by applying inverse operations.

 

 

You want k by itself on one side of the equation, you do this by dividing both sides by "half x squared".

 

 

This should yield k = 2*E / x^2

 

then substitute values for E and x in.

 

 

You might also need units for the constant k which are Joules / metres squared = kg / s^2 = N / m

 

 

I assume this is preparation for AS91168 Year 12 / NCEA Level 2 Physics in which case units are required.

 

 

More information about what is required in the standard here: http://www.nobraintoosmall.co.nz/html/senior_physics/NCEA2_physics_investigation.html

 

 

AS91168 involves a year long portfolio (usually 3 or 4) of investigating relationships in physical quantities.

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Geek
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  Reply # 1953904 8-Feb-2018 21:57
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So you need to isolate K:

 

1) Multiply both sides of the equation by 2: 2Ep=Kx(squared)

 

2) Divide both sides of the equation by x(squared): 2Ep/x(squared) = K

 

3) K = 2Ep/x(squared)

 

3) K = (2x 398J)/(0.045m)(squared)

 

4) K = 796 / 0.002025 (in units of J/m(squared))

 

5) K = 393086 J/m(squared)


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Ultimate Geek
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  Reply # 1953909 8-Feb-2018 22:05
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16 year olds do physics? I thought it was a secondary school thing...


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  Reply # 1953965 8-Feb-2018 22:53
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Thanks for reminding me why I hated Physics...!





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  Reply # 1953976 8-Feb-2018 23:17
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Starscream122:

 

16 year olds do physics? I thought it was a secondary school thing...

 

 

16 year olds are in secondary school.





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  Reply # 1953983 9-Feb-2018 00:27
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sonyxperiageek:

 

Starscream122:

 

16 year olds do physics? I thought it was a secondary school thing...

 

 

16 year olds are in secondary school.

 

 

Lmao my bad!


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  Reply # 1954002 9-Feb-2018 07:32
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beenz:

 

So any of you good at physics out there.

 

My 16 year old has asked me for help with his homework which is WAY over my head :)

 

 

 

So this is is it.....can you explain as well so we can both understand

 

 

 

Ep=1/2 Kx2 .......the two should be above the x as in squared

 

 

 

Use the equation to find K were Ep = 398J x=0.045m

 

 

 

Thanks

 

 

To me this looks like maths, not physics.





Most of the trouble in the world is caused by people wanting to be important. (T.S. Eliot)


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  Reply # 1954003 9-Feb-2018 07:46
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floydbloke: To me this looks like maths, not physics.

 

 

Physics is just applied maths.

 


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  Reply # 1954033 9-Feb-2018 08:45
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Or put another way: an engineer thinks that the numbers approximate reality; a scientist thinks reality approximates the numbers; a mathematician doesn't realise there is a connection


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  Reply # 1954036 9-Feb-2018 08:55
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Starscream122:

 

16 year olds do physics? I thought it was a secondary school thing...

 

 

 

 

That is secondary school or high school as it is called now.....





 


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