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Unformatted text preview: Physics 204 Homework 1 2. (Ch 8, MC 3) The answer is (c). One can compute the electric forces using the Coulomb’s law, using that an electron has charge q =- e , a proton has q = + e , an Na + ion has q = + e , and an SO 2 − 4 ion has q =- 2 e , where e = 1 . 60 × 10 − 19 C. Actually, it is much simpler if one is only interested in the ratio of the forces. Ac- cording to Coulomb’s law, the magnitude of the electric force between two charges is proportional to the product of charges and inversely proportional to the square of the distance between them. Compared to the e − –Na + pair, the P–SO 2 − 4 pair has twice the product of charges but also twice the distance. Thus, the magnitude of the electric force of the P–SO 2 − 4 pair is 2 / 2 2 = 1 / 2 as large as that between the e − –Na + pair. 3. (Ch 8, MC 6) The answer is (c). The force on 3 is produced by 1 and 2. The force of 1 is directed to the right and that of 2 is directed to the left, and because the net force...
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- Spring '09
- Physics, Electric charge, 1 m, 1.5 m, 0.6 m, 1.3 m