I really need help. I have no idea where to start with thisproblem. A molecule o

Question

I really need help. I have no idea where to start with thisproblem.

A molecule of DNA (deoxyribonucleic acid) lies along a straightline. It is 2.656 m long. The ends of the molecule becomesingly ionized; negative on one end, positive on the other. Thehelical molecule acts as a spring and compresses 0.5% upon becomingcharged.

The Coulomb constant is 8.99 × 109 N · m2/C2.

Determine the effective spring constant of the molecule. Take intoaccount the com- pressed length when calculating the distancebetween the ends of the molecule.

Answer in units of N/m.

Explanation / Answer

I would solve this problem for the force from the charges andthen use that force in the spring equation to get the springconstant. Since both ends are slightly charged, I gave them theelementary charge each. The distance that I used was the 0.5%compression distance. F = kq1q2/r2 = 8.99*109 * 1.6*10-19 * 1.6*10-19/(2.643*10-6m)2 = 3.29*10-17N F = kx - I used the compression for x k = F/x = 3.29*10-17 /(0.01328*10-6) =2.0*10-9N/m Hope that helps

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