Force on 3 current carrying wires

[jmr423]

Homework Statement

Two long fixed parallel wires, A and B, are 10cm apart in air and carry 40 A and 20 A, respectively, in opposite directions. Determine the resultant field (a) on a line midway between the wires parallel to them and (b) on a line 8.0 cm from wire A and 18cm from wire B (c) what is the force per meter on a third long wire, midway between A and B and in their plane, when it carries a current of 5.0A in the same direction as the current in A?

Homework Equations

F=BILsin(angle)
B= (2(10^7)I)/r

The Attempt at a Solution

I have solved part (a) and (b) i need help with (c) I have calculated the forces on them
A on C = 1E-4 towards
B on C = 2.2E-5 away

I tried to calculate it as though its on a straight line and also as though its making a triangle. for the triangle i used the angle ACB through the distances i have in cm. but it did not work.

Answers A) 2.4E-4T, B7.8E10-5T C 1.5E-3N/, toward A

 

[tiny-tim]

hi jmr423!

Two long fixed parallel wires, A and B, are 10cm apart in air
…
(c) what is the force per meter on a third long wire, midway between A and B and in their plane, when it carries a current of 5.0A in the same direction as the current in A?
…
I tried to calculate the angle ACB through the distances i have in cm. …

what angle?

they're all in the same plane ​

 

[jmr423]

hi jmr423! what angle?

they're all in the same plane ​

:S when i treat it as though its on a plane i get no where... i have tried a bunch of different things and nothing is working to solve c.

 

[tiny-tim]

show us what you've tried (in the same plane)