THE INTERNET PLASMA PHYSICS EDUCATION EXPERIENCE

Coulomb Force vs. Velocity!


In this experiment, you can study the relationship between kinetic energy and the Coulomb force. The four buttons in the experiment are "rewind", "stop", "play", and "step". Imagine that the spheres are glue-covered metal balls that will stick together if they meet. Time and the position of each sphere is presented in the Data box. Your variables are kinetic energy (remember: K.E.=1/2 x m x v2) and charge (the greater the charge of each particle the stronger the two masses repel each other due to the Coulomb force).

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(If you don't have shockwave, here's what you would see if you did.)

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Here are 2 questions to think about as you perform this experiment.
  1. What happens when you increase the kinetic energy and keep the charge constant?
  2. What happens when you increase the charge and keep the kinetic energy constant?

Can you find two different settings for which the spheres almost meet? For example, try setting Kinetic Energy to 10 Joules and finding the Coulomb Force that will make them almost meet. Then double both values and see what happens. Do you have any idea why?

(For extra credit) To further analyze the relationship between the Coulomb force and the distance between the two balls, you could plot this data on graph paper, or in a spreadsheet program. Step through and record your data. "t" is the time, in seconds. "X2" and "X3" is the location, in meters, of the balls. Does it look like the Coulomb force gets stronger as the balls get closer? If you cut the distance between in half does the force double or quadruple?

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