Two nonconducting spheres problem

  • Thread starter Thread starter n77ler
  • Start date Start date
  • Tags Tags
    Spheres
AI Thread Summary
The problem involves two nonconducting spheres with a total charge of 13.4 μC and a repulsive force of 2.777 N when separated by 0.362 m. The correct equations to use are Coulomb's law, F = k(q1)(q2)/r^2, and the total charge equation, q1 + q2 = 13.4 μC. A user attempted to solve for the charges but encountered issues with the equations, particularly with a typo in the total charge equation. After deriving a quadratic equation, they found potential values for q2 but still did not arrive at the correct answer, indicating a misunderstanding in the application of the equations. Clarification on the equations and their correct usage is needed to resolve the issue.
n77ler
Messages
89
Reaction score
0

Homework Statement



Two nonconducting spheres have a total charge of 13.4 μC. When placed 0.362 m apart. the force of repulsion is 2.777 N. What is the value of the greater charge (Give your answer in coulombs)?

Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
Hint: Coulomb's law.
 
I tried this equation below because I just put in the total charge for Q and got the wrong answer. I don't understand how I get answers for two different charge swhen I work through it.
E= k (q1+q2) / r^2
 
well first equation is F = K(q1)(q2)/r^2 and second equation is q1q2=13.4 μC
2 equations 2 unknowns.
 
tongpu said:
well first equation is F = K(q1)(q2)/r^2 and second equation is q1q2=13.4 μC
2 equations 2 unknowns.
You are correct, but that second equation has a typo: it should be q1 + q2 = 13.4 μC
 
F=kq1q2 / r^2 q1 + q2 = 13.4x10^-6C
2.777= (8.99x10^9)q1q2 /(0.362)^2
q1q2=4.05x10^-11
q1=(4.05x10^-11)/ q2

(4.05x10^-11)/q2 + q2 = 13.4x10^-6C
(4.05x10^-11)/ q2 + (q2^2)/q2 = 13.4x10^-6C
(4.05x10^-11) + (q2^2) = (13.4x10^-6C)q2
quadratic, when solved q2=4.60x10^-6, q2= 8.80x10^-6

Both of these numbers when added up will equal the total charge and when I sub them into the equation q1=(4.05x10^-11)/q2 I get the same thing. However this is not the correct answer, could someone point out where I went wrong?
 
Last edited:
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...
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...
Back
Top