• Support PF! Buy your school textbooks, materials and every day products Here!

Electrostatic Force Exerted Between Two Protons

  • Thread starter tjrana0
  • Start date
  • #1
3
0
A proton is in a vacuum near the surface of Earth. Where should a second proton be placed so that the electrostatic force it exerts on the first proton balances the weight of the first proton?

F = (k×Abs[q1]×Abs[q2]) / r^2
k = 8.99×10^9 Nm^2/C^2
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,230
31
You need to post your attempt.
 
  • #3
3
0
The first attempt, I got 1.51911E-14 which was incorrect.
It says "Did you use the Coulomb equation to get the electrostatic force? Do you recall how to calculate the gravitational force on an object (the weight) near Earth's surface?"
I did do all of the above, but with no success.

proton = 1.602176 10^-19;

Solve[1 == (k proton^2)/r^2, r]
{{r -> -1.51911*10^-14}, {r -> 1.51911*10^-14}}
This was the answer that was incorrect.
I thought that the left side of the equation was 1, for some reason, I'm not sure. If it is 0, then the equation is unsolvable. What did I do wrong?
 
  • #4
rock.freak667
Homework Helper
6,230
31
The first attempt, I got 1.51911E-14 which was incorrect.
It says "Did you use the Coulomb equation to get the electrostatic force? Do you recall how to calculate the gravitational force on an object (the weight) near Earth's surface?"
I did do all of the above, but with no success.

proton = 1.602176 10^-19;

Solve[1 == (k proton^2)/r^2, r]
{{r -> -1.51911*10^-14}, {r -> 1.51911*10^-14}}
This was the answer that was incorrect.
I thought that the left side of the equation was 1, for some reason, I'm not sure. If it is 0, then the equation is unsolvable. What did I do wrong?
If it is near the surface of the Earth, then a gravitational force acts on it, its weight, mg.

You want the weight to be the same the electric force.

So you need to equate mg to the formula for the electrostatic force.
 
  • #5
3
0
I did 1.6762622*10^-27*9.80665 == 8.99*10^9*1.602*10^-19*1.602*10^-19/r^2
and solved for r and got the right answer! Thank you!

Solve[1.6762622*10^-27*9.80665 ==
8.99*10^9*1.602*10^-19*1.602*10^-19/r^2, r]
{{r -> -0.118471}, {r -> 0.118471}}

r=0.118471m
 
Last edited:

Related Threads for: Electrostatic Force Exerted Between Two Protons

Replies
2
Views
837
Replies
1
Views
1K
Replies
5
Views
472
Replies
1
Views
2K
Replies
3
Views
10K
Replies
0
Views
1K
Replies
3
Views
1K
  • Last Post
Replies
2
Views
8K
Top