Posted by **Meridith** on Thursday, September 1, 2011 at 6:16pm.

Consider three charges arranged as shown.

The picture is three particles in a horizontal line. There charges are represented below in order

A B C

+ + −

the distance from A to B is 4.4 cm. The distance from B to C is 4.6 cm

A=8.2 µC B=4.5 µC C=−4 µC

What is the magnitude of the electric ﬁeld strength at a point 1.5 cm to the left of the middle charge? The value of the Coulomb constant is 8.98755×10^9Nm2/C2.

Answer in units of N/C

What is the magnitude of the force on a −4 µC charge placed at this point?

Answer in units of N

I know we use F=KQ1Q2/r^2

I tried to set up 3 different forces and then add them together... I did not get it right.

Please help!