point charges, Q1 (4,0,-3) and Q2 (2,0,1). Q2 = 4 nC, find Q1 such that the a. electric field at (5,0,6) has no z component.(adsbygoogle = window.adsbygoogle || []).push({});

b. force on a test charge at (5,0,6) has no x component.

heres what i did for a:

i found the distance from Q1 to (5,0,6) to be the square root of 82

distance from Q2 to (5,0,6) to be square root of 34.

i than found the unit vectors.

multipled by the charges and set the z components equal.

so i had 9Q1/sqr rt 82 = - 4nc*5/sqr rt 34

ended up with Q1 = -3.41 nc. answer in the back of the book says -3.463

on the second part i found the two forces using (Q*Qt)/4*pi*Eo*R^2.

i than multiplied these by the unit vectors in the x direction and set one of them equal to negative the other and solved for Q1. i ended up with an answer of -48nC, the book says -18nC.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Need confirmation on a problem

**Physics Forums | Science Articles, Homework Help, Discussion**