Physics Question [Electrical Forces + Spring]?

Posted on 2014-04-14 06:39:00 in Physics by HENRY

Problem

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A strand of DNA is 3.169 micrometers long. Its ends become singly ionized, causing the DNA to compress. The DNA compresses 0.4%. Find the DNA strand's spring constant.



Coulomb's constant is given to be 8.99 x 10^9. We were told to look up the fundamental charge (1.602 x 10^-19).



What I've been doing which gets me the wrong answer

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I start by finding the distance between the two charges after compression (3.169 x 10^6 X 0.996) and that comes out to be 3.1563 x 10^6.



I then find the force of the charges using F = kq1q2 / r^2. q1 = q2 = 1.602 x 10^-19. I find that force and set it equal to the force in the F = -kX. I then solve, and got a spring constant value of 1.827 x 10^9.



Thanks for reading.

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