# Solving Three Charges: Find Force on Q2

• jmatthews1991
In summary, three charges, Q1, Q2, and Q3, are arranged in a straight line with Q2 at 0.323 m to the right of Q1 and Q3 at 0.125 m to the right of Q2. The values for Q1, Q2, and Q3 are given as 1.37 μC, -2.53 μC, and 3.43 μC respectively. Using the formula F=kq1q2 / r^2, the total force on Q2 can be calculated by finding the forces between Q1-Q2 and Q2-Q3 and adding them vectorially. In this case, the forces add up to 5.29 N directed
jmatthews1991

## 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 !?

jmatthews1991 said:

## 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?

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

jmatthews1991 said:

berkeman said:

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

jmatthews1991 said:
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.

## 1. What is the formula for calculating the force on Q2?

The formula for calculating the force on Q2 in the presence of two other charges is F = k * (q1 * q2) / r^2, where k is the Coulomb constant, q1 and q2 are the charges of the two other charges, and r is the distance between Q2 and the other charges.

## 2. How do you determine the direction of the force on Q2?

The direction of the force on Q2 can be determined by using the principle of Coulomb's Law, which states that like charges repel each other and opposite charges attract each other. So, if Q2 has the same charge as one of the other charges, the force will be repulsive, and if Q2 has the opposite charge, the force will be attractive.

## 3. Can you solve for the force on Q2 if the charges are not directly aligned?

Yes, the force on Q2 can still be calculated even if the charges are not directly aligned. The formula for calculating the force takes into account the distance between the charges, so it will still provide an accurate result even if the charges are not in a straight line.

## 4. What is the unit of measurement for the force on Q2?

The unit of measurement for the force on Q2 is Newtons (N), which is the standard unit for measuring force in the International System of Units (SI).

## 5. Is there a limit to the number of charges that can be included in this calculation?

No, there is no limit to the number of charges that can be included in this calculation. The formula for calculating the force on Q2 can be applied to any number of charges, as long as the distance between Q2 and each charge is known.

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