Unformatted text preview: Physics 152S Winter 2012
Tutorial 2 Questions 1. In the ﬁgure shown, a central particle of charge +10 nC is surrounded by a square array of
charged particles, separated by 5 cm, 10 cm, or 15 cm along the perimeter of the square. One
side of the square is 20 cm. What are the magnitude and direction of the net electrostatic
force on the central particle due to the other particles? Give your answer both in component
form, and as a magnitude and an angle (specify from which axis the angle is measured). 10 nC +10 nC +10 nC 5 nC
+5 nC
20 cm +5 nC
+10 nC
+5 nC
5 cm
+5 nC
+10 nC 5 nC 10 nC 2. (Knight example 26.4 p.803) Two positively charged particles q1 and q2 = 3q1 are 10 cm
apart. Where (other than at inﬁnity) could a third charge q3 be placed so as to experience
no net force?
3. (Math review) Write the binomial expansion of the following functions to ﬁrst order in
the small parameter: (a) 1/(1 + x) in the limit x → 0; (b) 1/(1 − x) in the limit x → 0;
(c) 1/(z 2 + R2 )3/2 in the limit R/z → 0; (d) z/(z 2 + R2 )1/2 in the limit R/z → 0; (e)
z/(z 2 + R2 )1/2 in the limit z/R → 0.
4. (Math review) Evaluate the following integrals using ”change of variables”:
∫ π/2 (a) sin(2x)dx
∫ 0
1 1
dx
2
0 (2x + 1)
∫√
(c)
x x2 + 1dx (b) ...
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 Spring '12
 kim
 Physics, Charge

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