Electric Potential of 2 Point Charges

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SUMMARY

The discussion focuses on calculating the speeds of two charged spheres, C and D, at the moment of collision using energy conservation principles. Sphere C has a charge of 2nC and a mass of 1g, while sphere D has a charge of -1nC and a mass of 2g, starting from a distance of 10mm. The relevant equations include the electric potential formula, V=(1/4πε₀) * Q/r, and kinetic energy, K=0.5 * mv². The key conclusion is that the total initial energy of the spheres must equal their total final energy, necessitating a re-framing of the energy conservation equation to account for both spheres collectively.

PREREQUISITES
  • Understanding of electric potential and Coulomb's law
  • Familiarity with kinetic energy equations
  • Basic knowledge of conservation of energy principles
  • Ability to perform calculations involving charge, mass, and distance
NEXT STEPS
  • Study the derivation of the electric potential formula, V=(1/4πε₀) * Q/r
  • Learn about conservation of energy in electrostatics
  • Explore the effects of charge and mass on motion in electric fields
  • Practice solving problems involving multiple charged particles
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This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of charged particles and energy conservation in electrostatics.

vforvirginia
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Homework Statement


The 2.1mm diameter spheres in the figure are released from rest. What are their speeds vc and vd at the instant they collide?

Spheres:
C has 2nC of charge and a mass of 1g.
D has -1nC of charge and a mass of 2g.
The starting distance between the two spheres is 10mm. Each sphere as a diameter of 2.1mm.

Homework Equations


V=(1/4pi*ε_0)*Q/r
Q is the charge and r is the distance between the two spheres.
K=.5*mv^2


The Attempt at a Solution


ΔKC+ΔUC = 0 = ΔKD+ΔUD
Ki for spheres C and D are 0 since the spheres begin at rest:
KCf+UCf-UCi=KDf+UDf-UDi

The rest of my attempt is basically putting the numbers in and solving for KCf in terms of KDf and then using that to get KDf. I just want to know if I am heading in the right direction.
 
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Hi vforvirginia! welcome to pf! :smile:

In your energy conservation equations you are comparing the energies of two different balls and making them equal. I think that should be re-framed as, the total energy of the balls initially is equal to their total energy at the end.
 

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