Particle Physics: Net Force on Charge q1 Calculation

AI Thread Summary
The discussion revolves around calculating the net force on charge q1 (2.0 nC) due to two other charges, q2 (-3.5 nC) and q3 (5.0 nC), positioned along the x-axis. The user initially struggles with the calculations, particularly the application of the force equation F = k(q1q2/r^2). After clarifying the values and units, the user successfully recalculates the forces exerted by q2 and q3, ultimately finding the correct net force to be 3.8 x 10^-4 N. The conversation emphasizes the importance of careful calculations and understanding the principles of electrostatic forces. The final answer confirms the user's corrected approach and understanding of the problem.
Amelia
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Homework Statement


Three point charges are located on the positive x-axis of a coordinate system. Charge q1 = 2.0 nC is 2.0 cm from the origin, charge q2 = -3.5 nC is 4.0 cm from the origin and charge q3 = 5.0 nC located at the origin.

What is the net force ((a)magnitude and (b) direction) on charge q1 = 2.0 nC exerted by the other two charges?.[/B]

Homework Equations


F= k (q1q2/r^2)

The Attempt at a Solution


I know that the direction (b) is 0 degrees as all the points are all located on the x-axis, I just can't figure out part (a). I keep mixing up my diagram so that when the equation is applied, my answer comes out incorrectly. Any help would be great! [/B]
 
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Superposition of two forces. Do them one at a time.
 
Bystander said:
Superposition of two forces. Do them one at a time.
Okay, so would it be...
F of 2 on 1 = 9*10^-6((-3.5*10^-6)*(-2*10^-6)/(0.04)^2 = 39.375 N (+ve therefore forces repel)
F of 3 on 1 = 9*10^-6((2*10^-6)*(-5*10^-6)/(0.02)^2 = -225N (-ve therefore forces attract)
F total = 39.375 - (-225) = 264.375 N
 
"n" means what? Like charges attract or repel?
 
Bystander said:
"n" means what? Like charges attract or repel?
'N' in the final result was for Newtons
 
Lower case "n," as in "nC."
 
Bystander said:
Lower case "n," as in "nC."
nC = nanocoulomb
 
"Nano" means what?
 
Bystander said:
"Nano" means what?

ohhh... 1*10^-9 not 1*10^-6 thank you I didn't even see that !
so the new solutions come out at
F of 2 on 1 = -0.000225 N
F of 3 on 1 =0.000039 N
So the final answer would be -0.000225 N - 0.000039 N = -2.46*10^-4 I just tried to enter that in and it still came out incorrect... I'm just not sure what I'm doing wrong
 
Last edited:
  • #10
Amelia said:
F of 2 on 1
4-2=?
 
  • #11
Bystander said:
4-2=?
4-2=2 but I'm not sure where that fits in..
 
  • #12
Amelia said:
F of 2 on 1 = 9*10^-6((-3.5*10^-6)*(-2*10^-6)/(0.04)^2 = 39.375
 
  • #13
Okay so it should be
F of 2 on 1 = 9*10^9((-3.5*10^-9)*(-2*10^-9)/(0.02)^2 = 0.000158 N
F of 3 on 1 = 9*10^9((2*10^-9)*(-5*10^-9)/(0.02)^2 = -0.00025N
Therefore, Ft= 0.000158-(-0.00025) = 3.8*10^-4 N

Which I just put in and it's correct! Thank you so much for your help! :) :)
 
  • #14
You are welcome. Things to remember: one step at a time; and, pay attention to details.
 
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