1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Three Charges and a Spring

  1. Oct 15, 2011 #1
    1. The problem statement, all variables and given/known data

    Charge Q1 is fixed to the ceiling by means of a spring with the spring constant D and is moved from its rest position (which is at y=h) by the two charges Q2. The gravitational force may be neglected.

    a) Determine the resulting force on Q1 in dependency of y.

    b) The distance of the two charges Q2 should now be zero (a=0). Determine the charge Q2 as a function of y so that the resulting force on the charge Q1 becomes zero.

    2. Relevant equations

    Field equations of radial electric fields, force of a spring.

    3. The attempt at a solution

    I do not really have an idea for a), for b) however I tried to equalize the electric force and the spring force and then I solved for Q2. That looked like this:
    [itex]Q_2=-\frac{D*4*\pi*\epsilon_0*y^3}{2*Q_1}[/itex]. Can this be right?

    Attached Files:

  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted