12.10. Electricity Problem Set http://www.ck12.org
- Two pith balls of equal and like charges are repulsed from each other as shown in the figure below. They both
have a mass of 2 g and are separated by 30◦. One is hanging freely from a 0.5 m string, while the other, also
hanging from a 0.5 m string, is stuck like putty to the wall.
a. Draw the free body diagram for the hanging pith ball
b. Find the distance between the leftmost pith ball and the wall (this will involve working a geometry
problem)
c. Find the tension in the string (Hint: usey−direction force balance)
d. Find the amount of charge on the pith balls (Hint: usex−direction force balance)
Answers to Selected Problems
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11. b. 1350 N c. 1350 N
- 1 × 109 N/C
- 9000 N
12.Fg= 1. 0 × 10 −^47 N andFe= 2. 3 × 10 −^8 N. The electric force is 39 orders of magnitudes bigger.
- 0 × 10 −^4 C