# Electric Forces

## Homework Statement

Three charges, Q1, Q2, and Q3 are located in a straight line. The position of Q2 is 0.323 m to the right of Q1. Q3 is located 0.125 m to the right of Q2
In the above problem, Q1 = 1.37 μC, Q2 = -2.53 μC, and Q3 = 3.43 μC. Calculate the total force on Q2. Give with the plus sign for a force directed to the right.

F=kq1q2 / r^2

## The Attempt at a Solution

I used the above formula to find the force for charge 1-2, and charge 2-3, and then added them together. I got the wrong answer.
My answers were: 0.29867 N + 4.99 N = 5.29 N
What am i doing wrong !?

berkeman
Mentor

## Homework Statement

Three charges, Q1, Q2, and Q3 are located in a straight line. The position of Q2 is 0.323 m to the right of Q1. Q3 is located 0.125 m to the right of Q2
In the above problem, Q1 = 1.37 μC, Q2 = -2.53 μC, and Q3 = 3.43 μC. Calculate the total force on Q2. Give with the plus sign for a force directed to the right.

F=kq1q2 / r^2

## The Attempt at a Solution

I used the above formula to find the force for charge 1-2, and charge 2-3, and then added them together. I got the wrong answer.
My answers were: 0.29867 N + 4.99 N = 5.29 N
What am i doing wrong !?

Q1 and Q3 are both positive, but on opposite sides. Would their forces add?

Q1 and Q3 are both positive, but on opposite sides. Would their forces add?

I added them

berkeman
Mentor
I added them

And got the wrong answer...

And got the wrong answer...

Yeah I got the wrong answer.. What did I do wrong? What should I do ?

berkeman
Mentor
Yeah I got the wrong answer.. What did I do wrong? What should I do ?

The force equation that you wrote in your original post (OP) is actually a vector equation. The forces have both magnitude and direction. You need to take that into account when you sum the forces to get the resultant.