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: Trapping atoms

  1. Mar 23, 2009 #1
    1. The problem statement, all variables and given/known data
    We addrewss a one dimensional system. An atom moves along the x-axis with a kinetic energy K = 0.5*m*v**2. In the range -x0<x<x0 the atom enters the trap, and is affected by a magnetic fiels. The interaction with the magnetic field gives rise to a potential U(x) which we model:

    for abs(x)>= x0, U(x) = U0
    for abs (x) < x0, U(x) = U0*abs(x)/x0

    a) Find the force F(x) on the atom from the magnetic field. Is this force conservative?

    Let us also assume that the atom is charged and also subject to a constant electronic force, F0 acting in the positive x-direction

    b) If the atom has kinetic energy K = 0 at x = 0, how laarge must F0 be in order for the atom to escape? And if the kinetic energy is K = U0/2 at x = 0, how large must F0 then be in order for the atom to escape.
    2. Relevant equations

    3. The attempt at a solution

    F = -dU/dx

    F = 0 for abs(x) >= x0
    F = U0/x0 for -x0<x<0
    F = -U0/x0 0for 0<x<x0

    The force is conservative for it is only dependent on the position

    b) Here I need some help.
    Is the idea that the force must give the atom larger total energy than u0?
    Last edited: Mar 23, 2009
  2. jcsd
  3. Mar 23, 2009 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Not sure if that would be the case or not.

    The way I think about it is, how is the potential modified due to the presence of the constant electrostatic force?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook