Jump to content

Electric Forces

Recommended Posts

I need help answering this question:


A chage +q is located at the origin, while an identical charge is located on the x-axis at x= +0.50m. A third charge of +2q is located on the x-axis at such a place that the net electrostatic force on the charge at the origin doubles, its direction remaining unchanged. Where should the third charge be located?


I need some pointers on how to answer the question.



Link to post
Share on other sites

Force = kQq/(r^2) Q=charge at point P and q=charge a distance r from P


So the initial force would equal k(Q^2)/.25


The problem specifies that the force doubles as a result of its placement. Thus, the force in question becomes 2k(Q^2)/.25 = 8k(Q^2)


Set this equal to the same force equation at the beginning


8k(Q^2) = kQq/(r^2) little q = 2Q by specification. as you can see, the Q^2 and k drops out and what is left is 8 = 2/(r^2)


You'll get two answers for R. Try to figure out which side of the charge placing 2Q will increase the force on the charge as opposed to counteracting the force due to the charge at 0.5 m

Link to post
Share on other sites

The goal here is not to do the homework for people who ask homework questions, but to help them do it for themselves. A service that sells homework solutions is basically facilitating plagiarism.

Link to post
Share on other sites

First work out the force at the origin due to the first 2 charges. Using the electrostatic force formula for point charges, Coulomb's law:




For more than one charge you add them together, so the first 2 charges force at the origin added together timesed by 2 should be = to the 3 charges added together..


Which is pretty much what chemhelper said.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.