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DNA Electric Force Problem

  1. Nov 16, 2007 #1
    A molecule of DNA (deoxyribonucleic acid) is 2.09 µm long. The ends of the molecule become singly ionized -- negative on one end, positive on the other. The helical molecule acts like a spring and compresses 1.13% upon becoming charged. Determine the effective spring constant of the molecule.

    equations that should be used are: F=kx and F=ke (Coulomb constant) q1q2 / r^2

    you can find x, the distance the spring is compressed by multiplying 2.09x10^-6 x .0113 = 2.3617x10^-8 m

    you can find the force by using coulomb's law; use have all the info to plug in except for the charges (q1 and q2). what are they? once you know the charges, you can solve for F and then plug into F=kx to solve for the spring constant. please help!
  2. jcsd
  3. Nov 16, 2007 #2
    nvm... i figured out the answer. the charges used are that of a proton and electron (1.6x10^-19)
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