Superposition of 3 forces on a point charge

  • Thread starter jenzao
  • Start date
  • #1
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Homework Statement



Four charges are placed on the corners of a rectangle. What is the resultant force on the positive charge (a = 1.5 m, b = 0.5 m, q = 1.1 × 10-9C)?
(see attached drawing)

Homework Equations


Im having problems summing the forces using superposition


The Attempt at a Solution


F = k(qq) / r^2

F1 = 4e-9 (r=1.5m)
F2 = 4e-8 (r=0.5m)
F3 = 4e-9 (r=1.58m)

then when i try to superimpose i get probs..
i put tail of F1 vector at origin, then put tail of F2 vector ontop tip of F1.
I do the same for F3.
then i draw line from tail of F1 to tip of F3.
this is equal to 2*F3.
= wrong

please help. it has to be something with doing superposition wrong i think??

Homework Statement





Homework Equations





The Attempt at a Solution

 

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Answers and Replies

  • #2
Redbelly98
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I'll suggest figuring out the horizontal and vertical component of each vector (using sine and cosine), and find the resultant by adding up components.
 
  • #3
jtbell
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F1 = 4e-9 (r=1.5m)
F2 = 4e-8 (r=0.5m)
F3 = 4e-9 (r=1.58m)

What is the direction of each of these vectors?

Also, you should check your arithmetic and keep more digits until you reach the final answers. For F1 I get 4.84e-9 which is a big difference!

Always keep more digits during the intermediate steps, until you reach your final answer, and only then round it off to the proper number of digits.
 
Last edited:

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