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

AI Thread Summary
The discussion centers on calculating the electrostatic force between two point charges using Coulomb's Law. The user calculates the force as approximately 1.3 x 10^10 N but receives an incorrect response from an online system. Other participants suggest verifying the units of the charges and consider the possibility of a bug in the grading system. The user confirms the charges are in Coulombs and plans to consult their professor for further clarification. The conversation highlights the importance of accuracy in unit conversion and significant figures in physics calculations.
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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