A positive charge of 5.30 μC is fixed in place. From a distance of 4.60 cm a particle of mass 5.60 g and charge +3.30 μC is fired with an initial speed of 80.0 m/s directly toward the fixed charge. How close to the fixed charge does the particle get before it comes to rest and starts traveling away?
As 3.3micro-coulomb charge reaches 5.3 micro coulomb charge, its kinetic energy will be converted into potential energy. At the nearest point, all the kinetic energy will be converted into potential energy.
Kinetic energy = (1/2)mv^2 = (1/2)*(5.6/1000)*80^2 = 17.92 J
Potential energy = Q1Q2/(4pi*ε0*R) were R is the distance between Q1 andQ2.
Hence, 17.92 = (5.3*10^-6)*(3.3*10^-6)/[4pi*(1/36pi*10^9*R)] = 0.15741/R
Or, R = (0.15741/17.92)*100 = 0.8784 cms.
So the minimum distance will be 0.8784 cms when 3.3 micro-coulomb charge will start reverting back.
I hope it will help. Kindly let me know any questions if you have.
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