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## beenz

363 posts

Ultimate Geek

Topic # 229131 8-Feb-2018 21:30

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

## danielparker

12 posts

Geek

393086.41975308646

Maybe..

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

DFP

## beenz

363 posts

Ultimate Geek

I need to know how you work it out though ?

## beenz

363 posts

Ultimate Geek

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

## yitz

1034 posts

Uber Geek

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.

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

## scherfie

38 posts

Geek

One person supports this post

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)

## Starscream122

471 posts

Ultimate Geek

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

## Geektastic

10628 posts

Uber Geek

Trusted

Thanks for reminding me why I hated Physics...!

## sonyxperiageek

2293 posts

Uber Geek

Trusted

3 people support this post

Starscream122:

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

16 year olds are in secondary school.

## Starscream122

471 posts

Ultimate Geek

sonyxperiageek:

Starscream122:

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

16 year olds are in secondary school.

## floydbloke

1575 posts

Uber Geek

3 people support this post

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.

Don't use 'beefstew' as a password.  It's not stroganoff.

## Behodar

6055 posts

Uber Geek

Trusted

3 people support this post

floydbloke: To me this looks like maths, not physics.

Physics is just applied maths.

## shk292

1381 posts

Uber Geek

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

## Coil

5519 posts

Uber Geek

Trusted

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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