Vernier Software and Technology
Vernier Software & Technology

Discharge Rate


Designers at your local science museum are perfecting an exhibit on electrostatic discharge. The exhibit involves two long "bifilar" pendula. Each pendulum has a conducting ping-pong ball of known mass hanging from a pair of long non-conducting threads. They want visitors to "charge" the balls using a Teflon rod stroked with fur and see what happens.

The designers plan to have a local sign made while the set up is being perfected. As a student intern at the science museum, you have been asked to help one of the designers estimate how long it will take for the charges to drain off the balls before they touch. In addition, the sign makers have been asked to report on approximately how much charge is on each ball after a visitor charges the balls and touches them together.


In this activity, you will

  • Use the laws of mechanics and Coulomb's Law to find the information the sign maker needs.

Software for Experiment

This experiment uses Logger Pro software for video analysis. The video for analysis is included with the lab book.

Physics with Video Analysis

See other experiments from the lab book.

1Rolling Ball
2Big and Small: How to Scale an Image
3Velocity Change
4Velocity and Speed
5Velocity and Acceleration
6Three Movies: Determining Constant Acceleration
7Demon Drop: A Mathematical Modeling Activity
8Jumping on the Moon
92D Vectors: Pool Ball Displacement, Velocity, and Speed
10Galileo's Projectile I: Using 17th Century Techniques
11Galileo's Projectile II: Using Contemporary Techniques
12Projectile Motion Vectors
13Frictional Slowing
14Impulsive Juggling
15Center of Mass Motions
16Finding a Spring Constant
17Net Work - Kinetic Energy Theorem
19Slinky Wave Speeds
20Superposition of Slinky Waves
21A Wave Pulse Equation
22Doppler Effect: Surface Water Waves
23Doppler Effect: Sound Waves
24A Heat Engine: Relating Work to the P-V Cycle
25Coulomb's Law for Two Charged Spheres
26Discharge Rate
27Electric Field Due to a Line of Charge
28Resistance and Ohm's Law
29Parallel Plate Capacitor: Potential Difference vs. Spacing
30Wiring Capacitors in Series and Parallel
31Using RC Decay to Determine Capacitance
32Exploring Faraday's Law
33Snell's Law of Refraction

Experiment 26 from Physics with Video Analysis Lab Book

<em>Physics with Video Analysis</em> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

Buy the Book

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