Question

A set of point charges is held in place at the vertices of an equilateral triangle of side 13.0 cm , as shown in the figure (Figure 1) .

Part A: Find the maximum amount of total kinetic energy that will be produced when the charges are released from rest in the frictionless void of outer space.

K= 1.80x10^-6 J

Part B. If the charges at the vertices of the right triangle in the figure are released, how much total kinetic energy will they gain?(Figure 2) .

I CANT FIGURE OUT PART B!!!!

Figure 1

figure2

Answer 1

Gain in KInetic energy is dKE = change in potential energy

dKE = -(k*q1*q2/r12)-(k*q2*q3/r23)-(k*q1*q3/r13)

dKE = -(9*10^9*4*2*10^-12/0.1)-(9*10^9*4*3*10^-12/sqrt(0.1^2+0.15^2))-(9*10^9*3*2*10^-12/0.15) =-1.67 J

So the final answer is gain in KE = 1.679 J