Total potential energy due to gravitational and electrostatic potential energyby bobred Tags: electrostatic, energy, gravitational, potential 

#1
Feb1011, 09:07 AM

P: 104

1. The problem statement, all variables and given/known data
Two dust particles are separated by 0.01m and of the same mass and charge, find the total potential energy 2. Relevant equations [tex]E_{el}=k\frac{q_1 q_2}{r}[/tex] [tex]E_{grav}=G\frac{m_1 m_2}{r}[/tex] [tex]r=0.01 m[/tex], [tex]q_1=q_2=1.1201\times10^{18} C[/tex] [tex]m_1=m_2=13\times10^{9} kg[/tex] Where G and k are the gravitational and Coulomb's constant respectively. 3. The attempt at a solution [tex]E_{el}=1.128\times10^{24} J[/tex] [tex]E_{grav}=1.128\times10^{24} J[/tex] Not sure whether it [tex]E_{tot}=E_{el}+E_{grav}[/tex] or [tex]E_{tot}=\leftE_{el}\right+\leftE_{grav}\right[/tex]? 



#2
Feb1011, 09:21 AM

PF Gold
P: 280

you have found the electric and gravitational field. now calculate the potentials. total will be the sum of the potentials, not sum of their magnitudes.




#3
Feb1611, 05:37 AM

P: 104

So the potential energy of the system is zero?




#4
Feb1711, 08:15 AM

PF Gold
P: 280

Total potential energy due to gravitational and electrostatic potential energy
why should it be zero?




#5
Feb1711, 08:41 AM

P: 104

Well I have found the electrostatic and gravitational potential energies
[tex]E_{el}=1.128\times10^{24} J[/tex] and [tex]E_{grav}=1.128\times10^{24} J[/tex] Is it not their sum? I'm taking [tex]r=0[/tex] as the particles being together and [tex]E_{pot}=0[/tex] at [tex]r=\infty[/tex] 


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