# Coulumb's Law and force between charge

• thrills4ever
In summary, the ball with the charge of -10Q exerts a force of -10N on the ball with the charge of +Q. The tension in the string is also -10N.
thrills4ever

## Homework Statement

A ball, which we can treat as a point charge, has a charge of +Q and a weight of 9.00 N. This ball is 50 cm away from a ball of charge -10Q, which is fixed in position. The +Q ball is 30 cm vertically below, and 40 cm horizontally, from the other ball, and the +Q ball is held in equilibrium at that position by a string which happens to be perfectly horizontal

Image: http://www.webassign.net/userimages/81225?db=v4net

1) What is the magnitude of the electrostatic force that the ball with the charge of -10Q exerts on the ball with the charge of +Q?

2) What is the magnitude of the tension in the string?

3) What is the value of Q?

## Homework Equations

Fn = mgcos0
Fe = k(q1)(q2)/r^2
Fw = mg

## The Attempt at a Solution

I know this problem needs to be broken down into components, so I started off trying to figure out how to break up the Forces by drawing a free body diagram. On the -10Q ball there is Fn pointing upwards and mg directed downwards correct? To get the diagonal force I have to use mgcos0 which becomes mg(30/50)...I do not know if this is correct because I am trying to sum up all the forces in the x direction and all the forces in the y direction. As for finding the tension, I know it involves the same kind of process but I am confused on where to start since I think I need the answer to 1). with that answer I will be able to find answer 3 using coulomb's law.

Thanks for all the help!

To answer part 1, why don't you just directly solve your second equation? You have q1, q2, and you can easily find r.

i don't know the value of q though.

Draw a free body diagram for +Q. Three forces are acting on +Q: the electrostatic force by -10Q, the force of gravity, and the tension in the string. Resolve the electrostatic force, Fe, into vertical and horizontal components. The vertical component of this force must be equal and opposite to the weight, and the horizontal component must be equal and opposite to the string tension. With these equations, Fe and T can be found.

chrisk thanks for the help, I figured it out in like 5 minutes..I can't believe didnt realize it before.

## 1. What is Coulomb's Law?

Coulomb's Law is a fundamental law of electrostatics that describes the force between two electrically charged particles. It states that the force of attraction or repulsion between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

## 2. How is Coulomb's Law related to the concept of electric fields?

Coulomb's Law is closely related to the concept of electric fields. The force between two charged particles can be thought of as the interaction between the electric field created by one particle and the other particle's response to that field. This allows us to understand the force between charged particles in terms of the electric field, which is a useful tool for analyzing more complex systems of charges.

## 3. How does distance affect the force between two charges according to Coulomb's Law?

According to Coulomb's Law, the force between two charges is inversely proportional to the square of the distance between them. This means that as the distance between two charges increases, the force between them decreases. In other words, the force between two charges decreases rapidly as they are moved farther apart.

## 4. Does Coulomb's Law only apply to point charges?

Coulomb's Law can be used to calculate the force between any two charged objects, as long as they can be approximated as point charges. This means that the objects are small enough and far enough apart that their size and shape do not significantly affect the calculation of the force between them.

## 5. How is Coulomb's Law used in real-world applications?

Coulomb's Law is used in many real-world applications, including the design of electronic devices, understanding the behavior of atoms and molecules, and in the field of electromagnetism. It also plays a crucial role in the study of electricity and magnetism and is essential for understanding the behavior of electric charges in a wide range of systems.

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