INSTRUCTOR’S SOLUTIONS MANUAL FOR SERWAY AND VUILLE’S COLLEGE PHYSICS NINTH EDITION, VOLUME 2

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ANSWERS TO MULTIPLE CHOICE QUESTIONS 1. To balance the weight of the ball, the magnitude of the upward electric force must equal the magnitude of the downward gravitation force, or qE = mg, which gi... ves E = mg q = ( ) 5.0 × 10−3 kg ( ) 9.80 m s2 4.0 × 10−6 C = 1.2 × 104 N C and the correct choice is (b). 2. The magnitude of the electric fi eld at distance r from a point charge q is E = keq r 2, so E = ( ) 8.99 ×109 N ⋅m2 C2 ( ) 1.60 ×10−19 C ( ) 5.29 ×10−11 m 2 = 5.14 ×1011 N C ∼ 1012 N C making (e) the best choice for this question. 3. The magnitude of the electric force between two protons separated by distance r is F = kee2 r 2, so the distance of separation must be r = ke e 2 F = ( ) 8.99 × 109 N ⋅ m2 C2 ( ) 1.60 × 10−19 C 2 2.3 × 10−26 N = 0.10 m and (a) is the correct choice. 4. The ball is made of a metal, so free charges within the ball will very quickly rearrange themselves to produce electrostatic equilibrium at all points within the ball. As soon as electrostatic equilibrium exists inside the ball, the electric fi eld is zero at all points within the ball. Thus, the correct choice is (c). 5. Choosing the surface of the box as the closed surface of interest and applying Gauss’s law, the net electric fl ux through the surface of the box is found to be Φ E = Qinside ∈ 0 = ( ) 3.0 − 2.0 − 7.0 +1.0 ×10−9 C 8.85 ×10−12 C2 N ⋅m2 = −5.6 ×102 N ⋅m2 C meaning that (b) is the correct choice. [Show More]

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