Calculating Charge Using Coulomb's Law

In summary, the conversation discusses finding the value of q when a -9.0 micro-coulomb charge is placed 0.12 cm from another charge in a vacuum, resulting in a force of 850 N between the two charges. The equation used is F = kq1q2/r2 and the correct answer is 1.5 x 10-8 C. The conversation also includes a discussion about squaring the radius and using the correct units in calculations.
  • #1
jaxtar
4
0

Homework Statement


When a -9.0 micro-coulomb charge is placed 0.12 cm from a charge q in a vacuum, the force between the 2 charges is 850 N. What is the value of q?


Homework Equations


F = kq1q2/r2


The Attempt at a Solution


q2 = Fr2/kq1
q2 = (850 N)(0.0012 m2)/(9.00 x 109 Nm2/C2)(-9.00 x 10-6 C)
q2 = -1.22 x 10-18 C

My question is am I doing this right? The answer that my book gives is 1.5 x 10-8 C.
 
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  • #2
It's radius squared right?
 
  • #3
Feldoh said:
It's radius squared right?

Yes it is sorry I corrected my work above! Thanks!
 
  • #4
Well since you now (correctly) squared the radius, what do you get as an answer?
 
  • #5
Feldoh said:
Well since you now (correctly) squared the radius, what do you get as an answer?

The answer that I get is -1.22 x 10-18 C. When I worked the question I had squared the radius.
 
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  • #6
Well, the answer I get is the same one your book gives, so you're probably doing something wrong with the math. I'm not sure where that 10-18 is coming from...
 
  • #7
Thanks for all your help! It was me trying to put too much info into my calculator at once. If I break it up figure out the top then figure the bottom and divide I get the right answer except mine is negative.

Thanks again!
 

FAQ: Calculating Charge Using Coulomb's Law

1) What is Coulomb's Law?

Coulomb's Law is a fundamental law in physics that describes the electrostatic interaction between two charged particles. It states that the force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

2) How can Coulomb's Law be rearranged?

Coulomb's Law can be rearranged in two different ways. The first rearrangement involves solving for the force by multiplying both sides of the equation by the distance squared and then dividing by the charge of one of the particles. The second rearrangement involves solving for the distance by dividing both sides of the equation by the force and then taking the square root.

3) What is the significance of rearranging Coulomb's Law?

Rearranging Coulomb's Law allows us to solve for different variables depending on what information is given. This is helpful in various applications, such as calculating the force between charged particles or determining the distance between two charged objects.

4) Can Coulomb's Law be used to calculate the force between multiple charged particles?

Yes, Coulomb's Law can be extended to calculate the force between multiple charged particles. In this case, the force between each pair of particles can be calculated using the original form of Coulomb's Law, and then the vector sum of these individual forces can be calculated to find the net force on each particle.

5) How is Coulomb's Law related to Newton's Law of Universal Gravitation?

Coulomb's Law and Newton's Law of Universal Gravitation are both inverse-square laws that describe the force between two objects. However, Coulomb's Law applies to the electrostatic force between charged particles, while Newton's Law applies to the gravitational force between massive objects. Both laws demonstrate the relationship between force, distance, and the properties of the objects involved.

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