I've been trying to figure this problem out for quite awhile but am really struggling, help would be much appreciated. Thank you In the diagram to the right, the net force on the 1.0 mC charge is zero. What is the sign and magnitude of the unknown charge q? So the diagram is a triangle, which has two charges on the bottom, each 2.0mC, and 8 cm apart. The top is the unknown q, which from the middle of the triangle is 6cm up. And there is a 1.0mC charge in the centre of the triangle which is 3 cm up. (I have attached the diagram) Based on the measurements given, I'm first trying to come up with the x and y components for each of the forces. And this is where I'm already having difficulties. Q1 is bottom left, Q2 unknown top, Q3 bottom right, Q4 centre F12 = -F12xcos(theta)- F12ysin(theta) F13 = -F13x F14 = -F14xcos(theta)+ F14ysin(theta) x: -F12cos(theta)- F13 + F14cos(theta) = 0 y: -F12sin(theta) + F14sin(theta) = 0 Can anyone tell me if this looks remotely ok so far?