• Support PF! Buy your school textbooks, materials and every day products Here!

Vector problem with electricity

vector problem with electricity :(

Ok, so i am having problems with my vectors in two homework problems (or maybe i went wrong some where else)...

#1) Four identical point charges (q = +10.0 µC) are located on the corners of a rectangle. The dimensions of the rectangle are L = 70.0 cm and W = 25.0 cm. Calculate the magnitude and direction of the net electric force exerted on the charge at the lower left corner by the other three charges.

ok, so i drew a lovely picture of the rectangle with all three force vectors as repulsion. my work goes something like this:
F1= 8.99e9 * 10e-6 ^2 / .025^2 = 1438N
F2= 8.99e9 * 10e-6 ^2 / (.025^2+ .07^2) = 163N
F3= 8.99e9 * 10e-6 ^2 / .07^2 = 183.5N

Then made a vector table:

F1 x components = 0 and y components = 1438N
F2 x components = 163cos19.65= 153N y components...=54.7N
F3 x components = 183.5 N and y = 0

I then added up the x to get Fx=337N and Fy=1493N

then F= (337^2 + 1493^2) ^1/2 = 1530N (but thats wrong)

but then i got the angle by taking hte inverse tan of 1493/337 = 257degrees and that is correct, so i dont really know why my force magnitude is worng.... and i have another problem on my hw that is similar and i keep getting it wrong too, so i think i am doing something wrong with my vectors... any ideas or help would be greatly appreciated. THANKS!!
 

Answers and Replies

Check your unit conversions (specifically going from centimeters to meters).
 

Related Threads for: Vector problem with electricity

Replies
1
Views
5K
Replies
3
Views
5K
Replies
3
Views
2K
Replies
4
Views
2K
  • Last Post
Replies
3
Views
1K
Replies
0
Views
7K
Replies
3
Views
5K
Top