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# How do you work out Elastic strain energy in AS Physics? Watch

1. Can someone tell me how to work out elastic strain energy for Physics AS?? Please someone explain for me its doing my head in..

2. Basically its Work done= Force x Distance moved

so you use the equasion DeltaW=FDeltaL (Delts being that triangle.. change in)
3. (Original post by Keiran:.)
Basically its Work done= Force x Distance moved

so you use the equasion DeltaW=FDeltaL (Delts being that triangle.. change in)
ok thanks, so what do u use the equation half ke squared for?
4. (Original post by mujahid_e3)
ok thanks, so what do u use the equation half ke squared for?
When you stretch a spring a distance x, the tension goes from 0 to kx, where k is the spring constant.
Work done is force times distance, but the force was not constant.
So we use the average force while the spring was being stretched.
It went from 0 to kx so the average force was ½kx
Multiply by the distance and you get ½kx times x
½kx²
5. (Original post by Stonebridge)
When you stretch a spring a distance x, the tension goes from 0 to kx, where k is the spring constant.
Work done is force times distance, but the force was not constant.
So we use the average force while the spring was being stretched.
It went from 0 to kx so the average force was ½kx
Multiply by the distance and you get ½kx times x
Thanks so in whcih cases do i use each formula?? When do i use ½kx² and when do i use ½ke??

thanks!
6. (Original post by mujahid_e3)
Thanks so in whcih cases do i use each formula?? When do i use ½kx² and when do i use ½ke??

thanks!
x and e can both usually stand for extension in the equations.
The equation with extension in it is ½kx² or ½ke² for strain energy.

I don't recognise the formula ½ke. Where has it come from?
7. I suspect that the other expression is supposed to be ½Fx - that is, half of the tensile/compressive force times the extension/compression. So, the choice is between ½Fx and ½kx². As for which one to use - it depends what you know in the particular question you are set. It should be clear from context.

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Updated: December 1, 2010
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