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- PHY102 Physics II © Dr.Cem Özdoğan
- 4 point charges (each +Q and equal mass) are connected by strings, forming a square of side L.
- If all four strings suddenly snap, (i) what is the kinetic energy of each charge when they are very far apart? (ii) If each charge has mass m, find the velocity of each charge long after the string snaps.
- Use conservation of energy (Kf+Uf=Ki+Ui):
- (Final Kf of all four charges) = (Ui stored) =
- (energy required to assemble the system of charges)
- No energy needed to bring in first charge: U1=0
- Energy needed to bring in 2nd charge:
- Energy needed to bring in 3rd charge:
- Total potential energy is sum of all the individual terms shown on right hand side:
- So, final kinetic energy of each charge =>K=mv2/2 =
- 24-11 Electric Potential Energy of a System of Charged Particles
- Energy needed to bring in 4th charge: