Understanding Coulomb's Law: A Homework Help Guide

So you should indeed get a number around 1.52 x 10^10.Now you need to set that equal to the tension in the string...What do you know about the tension in a string that is being pulled (taut)? Are there any other forces involved that might be "helping" the tension pull on the string?In summary, two metal balls, A and B, with charges q and 2q respectively, are floating at rest on Space Station Freedom and connected by a taut thread of length 1.30 m. With each ball 1.66 m away from a bulkhead, the electrostatic force between them can be calculated using Coulomb's Law. Setting this force equal to the tension in
  • #1
jayz618
27
0
Coulombs Law ! Please Help

Homework Statement




Two metal balls A and B of negligible radius are floating at rest on Space Station Freedom between two metal bulkheads, connected by a taut nonconducting thread of length 1.30 m. Ball A carries charge q, and ball B carries charge 2q. Each ball is 1.66 m away from a bulkhead.
(a) If the tension in the string is 4.00 N, what is the magnitude of q?
(b) What happens as time passes ?

Homework Equations



F= Ke x q1 q2/r2

The Attempt at a Solution



I know the constant for Ke = 8.9875 x 10 9 N*m2/c2

And know the distance between the two objects is held together by a string with a certain tension of 4 N.

Quite honestly, I don't even know where to begin. She says this is a simple problem, but I don't feel the same way :)

Any help or suggestions as to where I should start would be greatly appreciated !
 
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  • #2


Hi jayz618, welcome to PF!:smile:

Hint: Why not start by using the equation you posted under "relevant equations" to caluclate the electrostatic repulsion between the balls (Don't worry about the fact that you aren't given a numerical value for 'q', just leave it written as 'q')...What does Newton's third law tell you about the relationship between the tension in the string and the electrostatic repulsion?

P.S. This level of problem should really be posted in the introductory physics help forum in the future.
 
  • #3


So 8987500000 x q x 2q/1.30 m ?

Im really lost, I can't get a response from my professor for any help.

Is that the proper set up ?

And in the future i will post these over there :)
 
  • #4


jayz618 said:
So 8987500000 x q x 2q/1.30m?

Im really lost, I can't get a response from my professor for any help.

Is that the proper set up ?

Yes, that's the electrostatic force between the balls...Now ask yourself, "what force(s) cause the tension in the thread?":wink:

EDIT: You mean 8987500000 x q x 2q/(1.30m)^2, right?
 
  • #5


So for the force between the two balls, I have come up with 1.518 x 1010=q x 2q <--- should be the right number now :)

The tension in the thread is caused by both balls, A having half as much force as b ?

Am I going in the right direction ?
 
  • #6


Oops, you are absolutely correct.

I forgot to square the 1.30m.
 

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 is Coulomb's Law mathematically expressed?

Coulomb's Law is expressed as F = k * (q1 * q2) / r2, where F is the force, k is the Coulomb's constant (9 x 109 N*m2/C2), q1 and q2 are the charges of the two particles, and r is the distance between them.

3. What are the units of Coulomb's constant?

The units of Coulomb's constant, k, are N*m2/C2. This can also be expressed as kg*m3/s2*C2.

4. How does distance affect the strength of the electrostatic force?

According to Coulomb's Law, the force between two charged particles is inversely proportional to the square of the distance between them. This means that as the distance between two charged particles increases, the force between them decreases.

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 deals with the electrostatic force between charged particles, while Newton's Law of Universal Gravitation deals with the gravitational force between massive objects.

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