Register to reply

Magnitude of electric force

by bastige
Tags: electric, force, magnitude
Share this thread:
bastige
#1
Mar23-08, 07:19 PM
P: 15
1. The problem statement, all variables and given/known data
Four point charges are placed at the four corners of a square. Each side of the square has a length L.
Find the magnitude of the electric force on q2 due to all three charges q1 , q2 , q3
and q4. Given L=1 and q= 1.38 μC. Answer in N


http://rs209gc2.rapidshare.com/files...f5e75220df.jpg
Photo of problem ^

2. Relevant equations



3. The attempt at a solution
http://rs220l32.rapidshare.com/files...3_19-17-38.jpg
Photo of work ^
Phys.Org News Partner Science news on Phys.org
Experts defend operational earthquake forecasting, counter critiques
EU urged to convert TV frequencies to mobile broadband
Sierra Nevada freshwater runoff could drop 26 percent by 2100
dynamicsolo
#2
Mar24-08, 05:48 PM
HW Helper
P: 1,662
Since you give units of N and microcoulombs in your statement, you are presumably working in SI units. Right off, I'd say check your value for k: I believe it is off by three orders of magnitude... (In your statement, I think you want the net force on q2 from the other three charges, so you don't want to type 'q2' again...)

Also, watch your forces and components. For starters, what is the distance along the diagonal of the square? What is the force between the diagonally opposed charges?
bastige
#3
Mar25-08, 06:07 PM
P: 15
Well the diagonal is also 1. K should = 8.99E9. I still get the wrong answer.

dynamicsolo
#4
Mar25-08, 07:13 PM
HW Helper
P: 1,662
Magnitude of electric force

Quote Quote by bastige View Post
Well the diagonal is also 1. K should = 8.99E9. I still get the wrong answer.
If the side of a square is 1, how long is the diagonal?
bastige
#5
Mar25-08, 08:50 PM
P: 15
A^2 + B^2 =c^2
1^2+1^2=c^2
2=c^2
1=c
Snazzy
#6
Mar25-08, 09:06 PM
P: 459
Square root of 2 is 1?
bastige
#7
Mar25-08, 09:49 PM
P: 15
Quote Quote by Snazzy View Post
Square root of 2 is 1?
hmm...good point, guess i shouldn't do this in my head. well, its 1.41421. Where Do i need to use it? I didn't have r in my final formula? where did i go wrong?
dynamicsolo
#8
Mar25-08, 09:54 PM
HW Helper
P: 1,662
Quote Quote by bastige View Post
hmm...good point, guess i shouldn't do this in my head. well, its 1.41421. Where Do i need to use it? I didn't have r in my final formula? where did i go wrong?
The value for c you just calculate is what you will use in Coulomb's Law for the force between the diagonally opposite charges. Since the formula calls for r^2, you could use r^2 = 2 there.
bastige
#9
Mar25-08, 10:11 PM
P: 15
Quote Quote by dynamicsolo View Post
The value for c you just calculate is what you will use in Coulomb's Law for the force between the diagonally opposite charges. Since the formula calls for r^2, you could use r^2 = 2 there.

??????I'm sorry, I'm physics illiterate
dynamicsolo
#10
Mar26-08, 01:55 PM
HW Helper
P: 1,662
You have the equation for the force

kqq/(r^2) , which is Coulomb's Law.

In the image you show for your work, the force for the "southeast" diagonal should be using 2 in the denominator, instead of 1, since the distance squared between the two charges q2 and q4 is 2 .


Register to reply

Related Discussions
MAgnitude of electric Field Advanced Physics Homework 1
Magnitude and direction of electric force (file attached) Introductory Physics Homework 6
Magnitude of an electric force problem with vectors Introductory Physics Homework 3
Magnitude of Electric Field Introductory Physics Homework 9
How to calculate the magnitude of force when some force is applied at far away distan Mechanical Engineering 1