[填空题]
The two strands of the helix-shaped DNA mol gzfd u:r6:wz ;fk)q-ii)bk0tecule arep .enlj *(hi(z held together by electrostatic forces as shown in Fig. 16–44. Assume that the net average charge (due to electron sharing)zl (p.(e*hnji indicated on H and N atoms is 0.2e and on the indicated C and O atoms is 0.4e. Assume also that atoms on each molecule are separated by $ 1.0\times10^{ -10}\,m$. Estimate the net force between
(a) a thymine and an adenine; $ \times10^{-10 }\,N$
(b) a cytosine and a guanine. For each bond (red dots) consider only the three atoms in a line (two atoms on one molecule, one atom on the other). $ \times10^{-10 }\,N$
(c) Estimate the total force for a DNA molecule containing $10^5$ pairs of such molecules. $ \times10^{-5 }\,N$
