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Electric Forces

  • #1

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.


Homework Equations



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 !?
 

Answers and Replies

  • #2
berkeman
Mentor
56,660
6,559

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.


Homework Equations



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?
 
  • #3
Q1 and Q3 are both positive, but on opposite sides. Would their forces add?
I added them
 
  • #4
berkeman
Mentor
56,660
6,559
  • #5
And got the wrong answer...
Yeah I got the wrong answer.. What did I do wrong? What should I do ?
 
  • #6
berkeman
Mentor
56,660
6,559
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.
 

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