# Superposition of 3 forces on a point charge

## 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

## The Attempt at a Solution

#### Attachments

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Redbelly98
Staff Emeritus
Homework Helper
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.

jtbell
Mentor
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.

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