What is the magnitude of the electrostatic force between two point charges?

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Homework Help Overview

The problem involves calculating the magnitude of the electrostatic force between two point charges, Q1 and Q2, using Coulomb's Law. The charges are specified as Q1 = -9.4 C and Q2 = 3.6 C, separated by a distance of 4.8 m.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of Coulomb's Law and the calculations involved. There is a focus on whether the charges are correctly expressed in Coulombs and the implications of significant figures on the final answer.

Discussion Status

Some participants express confidence in the calculations but question the accuracy of the online grading system. There is an exploration of potential issues related to the input format or expectations regarding significant figures.

Contextual Notes

Participants mention the possibility of misunderstanding the units of the charges and the significance of significant figures in the context of the problem.

therealkellys
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I've been working on the following problem but when I try my answer online, it keeps coming up as incorrect. A charge Q1=-9.4 C is 4.8 m from a charge Q2 = 3.6 C. What is the magnitude of the electrostatic force on Q1?

I'm pretty sure for this its just Coulomb's Law so:
F = (k(Q1*Q2))/r^2
F = ((8.9876*10^9)(-9.4*3.6))(4.8^2)
F ~ 1.32 * 10^10 N
Taking into account sig. figs, my final answer is 1.3*10^10 N. \

However, this keeps coming up as incorrect. Am I overlooking something? Thanks in advance for the help!
 
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therealkellys said:
I've been working on the following problem but when I try my answer online, it keeps coming up as incorrect. A charge Q1=-9.4 C is 4.8 m from a charge Q2 = 3.6 C. What is the magnitude of the electrostatic force on Q1?

I'm pretty sure for this its just Coulomb's Law so:
F = (k(Q1*Q2))/r^2
F = ((8.9876*10^9)(-9.4*3.6))(4.8^2)
F ~ 1.32 * 10^10 N
Taking into account sig. figs, my final answer is 1.3*10^10 N. \

However, this keeps coming up as incorrect. Am I overlooking something? Thanks in advance for the help!
Sounds right to me. Are you sure that the charges are given in Coulombs (and not microcoulombs or nanocoulombs)? Other than that, I can't see anything wrong.

Patrick
 
Yep, I just looked it over again and all charges are given in Coulomb's. I think I might email my professor to see if he can look it over. Perhaps its a bug in the online grading system? I'm fairly confident in my answer. Thanks for looking it over!
 
therealkellys said:
Yep, I just looked it over again and all charges are given in Coulomb's. I think I might email my professor to see if he can look it over. Perhaps its a bug in the online grading system? I'm fairly confident in my answer. Thanks for looking it over!
You are welcome. Yes, it might be a big. Or maybe the system is expecting an answer with 3 sig figs (even though the answer should really have only two sig figs). But your answer is correct.

Best luck!

Patrick
 

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