# Electricity: Static Electricity

## Static Electricity: Audio Guided Solution

#### Problem 29:

Two negatively-charged balloons with a mass of 1.78 g are suspended by threads from a common point on the ceiling. The two balloons repel to an equilibrium position in which the angle between the two threads is 13.1 degrees. The distance from ceiling to the center of either one of the balloons is 155 cm. Determine the charge on each balloon. Assume the same amount of charge is on each balloon.

## Habits of an Effective Problem Solver

• Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
• Identify the known and unknown quantities; record them in an organized manner. A diagram is a great place to record such information. Equate given values to the symbols used to represent the corresponding quantity - e.g., Q1 = 2.4 μC; Q2 = 3.8 μC; d = 1.8 m; Felect = ???.
• Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
• Identify the appropriate formula(s) to use.
• Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.