Having some trouble with an electric potential problem. I thought I understood it but I keep getting an infinity in the equation which just can't happen.(adsbygoogle = window.adsbygoogle || []).push({});

Three small spheres with charge 2.00 mC are arranged in a line, with sphere 2 in the middle. Adjacent spheres are initially 8.00 cm apart. The spheres have masses m1 = 20g, m2 = 85.0g and m3 = 20.0g, and their radii are much smaller than their separation. The three spheres are released from rest.

So from the last sentence I get the idea to treat it as 3 point charges.

For point charges potential = kq/r.

For the first question I need to find the acceleration on point 1.

My idea was to add up both forces applied to it by points 2 and 3. I used:

F = k*2.00mC/.08 + k*2.00mC/.16

F = ma so a = F/m But that gives me a = 168596338021 m/s^2 which doesn't work and seems rather large.

For the next 3 parts it wants me to find the velocity of each particle when they're far apart. The middle one is easy since its 0. The outter 2 will be equal but I can't seem to solve it without an infinity.

I know I will need to use K_1 + U_1 = K_2 + U_2.

I am not sure how to approach it since U = -QV, and V = the integral of k*q/r from r_0 to far away, aka infinity. Secondly, when U = -qV, what value to I use for Q and q??

Am I approaching this part wrong?

Thanks for the help.

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# Homework Help: Electric Potential, acceleration and velocity

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