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Hello, so this was a past assignment question that I attempted. I got the right answer but in an incorrect way (I guess my thinking was not based on the concept?)

Three point charges of charge Q = 10 https://maple-ta.uwaterloo.ca/mapleta/tmp/am/dh/gm/finnniaffjjcdncgjfhcnmebcf.gif [Broken] and mass m = 25 g are located at the corners of an equilateral triangle, with side length 4 cm. One of the charges is let go. Gravity should be ignored.

What will its speed be when it is at infinity?

The answer was 56 m/s

My solution was:

E1 =E2= Kq/r = ((8.99x10^9)(1x10^-5)(1x10^-5))/(0.04) = 22.475J

Then the x component was:

E1(x)= 22.475J*sin 30=11.2375

E2 (x)=22.475J*-sin 30=-11.2375

E1(y)=22.475J*cos30=19.46

E2(y)=22.475J*cos30=19.46

THen using Ke=1/2mv^2

v=56m/s

I used components instead of the electromagnetic force equation between two charges.

This is wrong or an incorrect way of thinking and I should've used the equation:

(kQQ/r-3KQQ/r)

Can someone explain to me what is going on and how this equation explains what is happening between the three forces.

Thanks

1. Homework Statement1. Homework Statement

Three point charges of charge Q = 10 https://maple-ta.uwaterloo.ca/mapleta/tmp/am/dh/gm/finnniaffjjcdncgjfhcnmebcf.gif [Broken] and mass m = 25 g are located at the corners of an equilateral triangle, with side length 4 cm. One of the charges is let go. Gravity should be ignored.

What will its speed be when it is at infinity?

The answer was 56 m/s

3. The Attempt at a Solution3. The Attempt at a Solution

My solution was:

E1 =E2= Kq/r = ((8.99x10^9)(1x10^-5)(1x10^-5))/(0.04) = 22.475J

Then the x component was:

E1(x)= 22.475J*sin 30=11.2375

E2 (x)=22.475J*-sin 30=-11.2375

E1(y)=22.475J*cos30=19.46

E2(y)=22.475J*cos30=19.46

THen using Ke=1/2mv^2

v=56m/s

I used components instead of the electromagnetic force equation between two charges.

This is wrong or an incorrect way of thinking and I should've used the equation:

(kQQ/r-3KQQ/r)

Can someone explain to me what is going on and how this equation explains what is happening between the three forces.

Thanks

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