How Do You Calculate the Charge and Number of Excess Electrons on a Pith Ball?

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SUMMARY

The discussion focuses on calculating the charge and number of excess electrons on a pith ball that weighs 3 grams and hangs at an angle of 20 degrees from the vertical due to the influence of a charged rod. The key equation utilized is Coulomb's Law, represented as kqq/r², where k is Coulomb's constant. Participants emphasize the necessity of drawing a free-body diagram and applying Newton's second law to establish two equations involving the unknown charge (q) and the tension (T) in the cord. The problem requires understanding the geometry of the situation and the forces acting on the pith ball.

PREREQUISITES
  • Understanding of Coulomb's Law (kqq/r²)
  • Basic knowledge of Newton's second law
  • Ability to draw and interpret free-body diagrams
  • Familiarity with trigonometric functions to resolve forces
NEXT STEPS
  • Study the principles of Coulomb's Law in detail
  • Learn how to construct and analyze free-body diagrams
  • Explore the application of Newton's second law in static and dynamic systems
  • Investigate the concept of electric charge and quantization of electrons
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Students in physics, particularly those studying electrostatics and mechanics, as well as educators looking for practical examples of force analysis in charged systems.

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Homework Statement


My problem states that a pith ball hangs at 20 degrees from the vertical and weighs 3 grams. It is moved 10cm by a charged rod. They both have the same charge. It asks what is the charge on the ball in C and approximatley how many excess electrons are on the ball.


Homework Equations


I have the equation kqq/rsquared


The Attempt at a Solution


I found all the sides to the triangle and I do not know where to go from there. I do not know the charges so how can I use the equation with q in it?
 
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ehdubbya said:
It is moved 10cm by a charged rod.

10 cm in which direction? x? y? other? And where is the rod in relation to the ball? Is the charge distributed over the entire rod, or is it concentrated at a point?



I found all the sides to the triangle and I do not know where to go from there. I do not know the charges so how can I use the equation with q in it?

Did you draw a free-body diagram and set up the equations from Newton's second law? You should have 2 equations in 2 unknowns (q and the tension T in the cord from which the ball hangs).
 

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