Can you check this? - Charges and Forces

  • Thread starter Albeaver
  • Start date
  • #1
5
0
Can you check this? -- Charges and Forces...

Homework Statement


A +3-mC charge and a -4-mC charge are fixed in position and separated by 5 meters.
A)Where could a +7-mC charge be placed so that the net force on it is zero?
B)Where could a -7-mC charge be placed so that the net force on it is zero?

I came up with this diagram:
|---------------5m------------------|
*----------------*------------------*
q[1] q[2] q[3]
|-------r[1]------|----------r[2]----|


Homework Equations


F[1]=K(|q[1]*q[2]|)/r[1]^2
F[2]=K(|q[2]*q[3]|)/r[2]^2
r[1]+r[2]=5
k=8.99*10^9
|q[1]|=4
|q[3]|=3
|q[2]|=7

The Attempt at a Solution


F[1]=F[2]<---Because they are equal
K(q[1]*q[2])/r[1]^2=K(q[3]*q[2])/(5-r[1])^2<---We get (5-r[1])=r[2] from r[1]+r[2]=5 solved for r[2])
Then after we solve for r[1] we get this:
r[1]=5*√(q[3])*(√(q[3])-√(q[1]))/(q[3]-q[1])

So that means that both the +7-mC charge and the -7-mC charge are in the same position. The number I got was r[1]=2.32m and r[2]=2.68m. Did I set this up, and execute this correctly?
Thank you very much for your time.
 

Answers and Replies

  • #2
796
44
With a +3 on the left and a-4 on the right, is there any position between the two where the net force will be zero? Maybe the position is to the left or right of both charges.
 

Related Threads on Can you check this? - Charges and Forces

  • Last Post
Replies
1
Views
7K
Replies
8
Views
534
  • Last Post
Replies
1
Views
4K
Replies
4
Views
716
Replies
2
Views
710
Replies
1
Views
645
  • Last Post
Replies
1
Views
2K
Replies
1
Views
6K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
1
Views
2K
Top