# Coulomb's Law Questions

1. Dec 13, 2012

### roske

Using Coulomb's Law, find the force between two objects that have charges of 5 Coulombs and 7 Coulombs, respectively. They are separated by a distance of 5 meters. For the same objects, one of which has a mass of 5kg and the other has a mass of 7kg, what is the force of gravity between them if they are also 5 meters apart? If the charges are both positive, what is the net force between them and in what direction will they initially be accelerated: toward each other or away?

Could somone help me with this question with explanations?

Would really appreciate it!

Extra Credit Question: What is the electrical potential field that an object with a charge of 25 Coulombs experiences if it encounters force of 9 Newtons?

2. Dec 13, 2012

### SammyS

Staff Emeritus
Before we can help, you need to share what your thoughts are regarding this problem. -- It's the rules here in Homework help.

3. Dec 13, 2012

### roske

F= k(5C*7C)/5meters

Obviously I have to use Coulomb's law. I am not sure how to integrate the masses of each object into the equation. The answer will be in Newtons. Since they are both positive charges they will be accelerating away from each other.

4. Dec 13, 2012

### SammyS

Staff Emeritus
The separation distance is squared in Coulomb's Law.

Do you know Newton's law of universal gravitation ? It looks much like Coulomb's Law, with the masses replacing the charges. The constants are very different.

http://en.wikipedia.org/wiki/Law_of_universal_gravitation

http://en.wikipedia.org/wiki/Coulomb%27s_law