Finding Equilibrium Charge in a Static System

AI Thread Summary
The discussion revolves around finding the charge q1 needed for charge q2 to be in static equilibrium with a given charge Q of -4.6nC. The participant initially struggles with applying Coulomb's Law and setting the forces to zero for equilibrium. They realize that using dimensional analysis could simplify the problem, particularly in understanding the effect of distance on force. After receiving guidance, they acknowledge overthinking the solution. The correct charge q1 is determined to be 18nC for the system to achieve static equilibrium.
LIZard137
Messages
3
Reaction score
0

Homework Statement



In the figure below the charge in the middle is Q = -4.6nC. For what charge q1 will charge q2 be in static equilibrium?

q1-----10cm------Q------10cm------q2

I know that the answer is supposed to be 18nC.

Homework Equations



F=Ke lq1llq2l/r2

The Attempt at a Solution



Since the charges are in static equilibrium, I'd assume that F=0. So...
0=(kel-4.6llq1l/102)+(kelq1lq2l/202)

I've tried several ways of working this problem with Coulomb's Law, but I just can't seem to find the initial step in the right direction.
 
Physics news on Phys.org
Hi LIZard137! :smile:

Just use dimensional analysis …

if you double the distance, what happens to the force? :wink:​
 
Wow I completely over thought that... Now I feel retarded lol. Thanks for the help.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Finding the charge when three charges are in equilibrium
Replies
5
Views
5K
Finding Equilibrium in Electric Fields of Two Charges
Replies
13
Views
3K
Coulomb's Law, what charge will make the two charges in static eq.
Replies
6
Views
20K
How to find distance between 2 charges, with no force given?
Replies
2
Views
2K
Physics problem on force of a charge
Replies
2
Views
2K
Finding the New Acceleration Given Point Charges
Replies
10
Views
6K
Force on a 3rd point charge due to 2 other point charges
Replies
5
Views
14K
Solve Columb's Law Problem: q1 for q2=4.4nC, Dist 10cm and 20cm
Replies
7
Views
14K
Electrostatic Force and Field between two charges
Replies
5
Views
2K
Electrostatics (four equal point charges)
Replies
14
Views
2K

Hot Threads

Recent Insights

Back
Top