- #1
Potatochip911
- 318
- 3
Homework Statement
I'm going through the derivation here starting on page 16. This image adds some context:
Generalizing their result to the i'th particle they find the extended distance between two masses being ##\Delta l= \frac{(y_i-y_{i-1})^2}{2a}## Then since the potential energy is given by force * displacement they obtain $$V_i=\frac{F}{2a}(y_i-y_{i-1})^2$$ where ##F## is the tension in the string.
However since the string is stretching Hooke's law should apply which then results in the potential being ##V_i=\frac{1}{2}kx^2##, I'm having trouble showing this produces the same result as above
Homework Equations
##F=-kx##, where x is the extended distance
The Attempt at a Solution
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Ignoring the sign convention and using ##F=kx## we sub into the potential equation and get ##V_i=\frac{1}{2}Fx##, but x is just the extended distance ##\Delta l## therefore $$V_i = \frac{F}{2}\frac{(y_i-y_{i-1})^2}{2a}=\frac{F}{4a}(y_i-y_{i-1})^2$$ so I've obtained an extra factor of 1/2 but I can't seem to figure out why