# Net Force Exerted on 4.0*10-9 C Charge at Origin

• undrcvrbro
In summary: The net force on the center charge is the sum of these two forces, which is negative because of the direction of the vector addition.
undrcvrbro

## Homework Statement

A 1.4*10-9 C charge is on the x-axis at x = -2.0 m, a 7.0*10-9 C charge is on the x-axis at x = 2.5 m. Find the net force exerted on a 4.0*10-9 C charge located at the origin.

## Homework Equations

F=k(q1*q2) / (r^2)
k= 9*10^9

## The Attempt at a Solution

I simply took the difference of the two Forces existing between the central charge and each end of the axis.
I took:
F= (9*10^9)(1.4*10^-9)(4.0*10^-9) / (2)^2
and then subtracted it from:
F= (9*10^9)(7.0*10^-9)(4.0*10^-9) / (2.5)^2

But that obviously isn't correct, because Web assign gave me a big red X when I plugged the answer in. Any help is greatly appreciated!

Force is a vector and the total force on the central charge can be found using vector addition. Work out what direction each force is acting and the answer should become apparent.

Kurdt said:
Force is a vector and the total force on the central charge can be found using vector addition. Work out what direction each force is acting and the answer should become apparent.

Yes, that's what I thought, but I got the wrong answer...I'm missing something here.

Because all vectors are on x axis, and its asking for the net force on the center charge, wouldn't I just take the force imposed on the center from the left, and subtract it from the force between the center and the right charge? It seems too simple.

undrcvrbro said:
Yes, that's what I thought, but I got the wrong answer...I'm missing something here.

Because all vectors are on x axis, and its asking for the net force on the center charge, wouldn't I just take the force imposed on the center from the left, and subtract it from the force between the center and the right charge? It seems too simple.

Because force is a vector it matters what direction it is acting in. Since all charges are positive the force is going to be repulsive. Draw a diagram if it helps.

So the left charge will produce a force that wants to push the centre charge to the right. The right charge will produce a force that wants to push the centre charge to the left. If we take right as the direction of the unit vector on the x-axis, then the force from the left charge will be a positive factor multiplied by the unit vector. The force from the right charge will be a negative factor of the unit vector. Now apply vector addition.

## What is the net force exerted on a 4.0*10-9 C charge at the origin?

The net force exerted on a charge at the origin can be calculated using Coulomb's Law, which states that the force between two charges is directly proportional to the magnitude of each charge and inversely proportional to the square of the distance between them. Therefore, the net force on a 4.0*10-9 C charge at the origin would depend on the magnitude and distance of any other charges present in the system.

## How do you calculate the net force on a charge at the origin?

To calculate the net force on a charge at the origin, you will need to know the magnitude and location of all other charges in the system. Then, you can use Coulomb's Law to determine the force between the charges. Once you have calculated the forces between all pairs of charges, you can add them together vectorially to determine the net force on the charge at the origin.

## What factors affect the net force on a 4.0*10-9 C charge at the origin?

The net force on a 4.0*10-9 C charge at the origin is affected by the magnitude and location of all other charges in the system. The distance between the charges also plays a significant role, as the force decreases with distance according to the inverse square law. Additionally, the presence of any conductive or insulating materials in the vicinity may also impact the net force on the charge.

## Can the net force on a 4.0*10-9 C charge at the origin be negative?

Yes, the net force on a charge at the origin can be negative. This would occur if the force exerted by another charge is opposite in direction to the force exerted by another charge. In other words, if the forces are acting in opposite directions, they will cancel each other out and result in a net force of zero or a negative net force.

## Is the net force on a 4.0*10-9 C charge at the origin affected by the charge's velocity?

No, the net force on a charge at the origin is not affected by the charge's velocity. Coulomb's Law only takes into account the magnitude and location of charges, not their velocities. However, the charge's velocity may impact the motion of the charge if there are other forces acting on it, such as magnetic or electric fields.

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