Does Anybody Know How To Do This Physics 2 Problem?

Question

Three positive charges are located in the x-y plane (see plot below), with Q1=4.10 μC, Q2=7.20 μC and Q3=8.30 μC. Note that the charges are located at grid intersections, and that the x and y coordinates are in cm. Also, 1 C = 10^6 μC and 1 m = 100 cm

A. Calculate the magnitude of the electric force on Q1 due to Q2. 7.80×10^1 N is the answer i already found for this part.

B. Calculate the x-component of the force on Q1 due to Q3.

I calculated the magnitude of the force to be 41.4 N but i don't know how to find the x-component of this force because i don't know the angle between the two charges.

http://i36.photobucket.com/albums/e12/lilbac2003/ThreeCharges.png

Answer 1

Ok, I won't do your homework for you, but it's pretty simple. You've got the magnitude to be 41.4 N. You got that by doing the distance/pythagoras theorem. Now just use ur trig skills to find the angle (you have the X and the Y... not that hard to use tangent, isn't it?)

then sub the angle and the magnitude into a cos equation. simple.