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: Algebra Clarification Requested - The Fate of an Electron in a Uniform Electric Field

  1. Jan 20, 2005 #1
    The electron, having been held at height h0, is now released from rest. Calculate its speed v when it reaches the top plate.

    I found the initial energy to be:


    and the final energy to be:


    And I need to solve for v, so I set the two equal to each other as per the conservation of energy thereom and solve for v, correct?

    -q_e*E*h_0 = 1/2*m*v^2+-q_e*E*h_1

    My problem is isolating v and cancelling/clearing up variables. My algebra is lagging a bit, admittedly. Thanks for any help.
  2. jcsd
  3. Jan 20, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    Pay attention with the signs...The skeleton of your equation is
    [tex] A=B+v^{2}C [/tex]

    Isolate v^{2} and then take root of second order...

  4. Jan 20, 2005 #3
    Thanks. I only get one shot at an answer (it's an online-based assignment), so I would appreciate any response saying if this is correct or not, and what I did wrong if it is incorrect:

    [tex] sqrt((2(h_0-h_1))/(m))=v[/tex]
  5. Jan 20, 2005 #4
    Can anyone else help me out please?

    EDIT: Nevermind, I got it.
    Last edited: Jan 20, 2005
  6. Jan 21, 2005 #5


    User Avatar
    Science Advisor
    Homework Helper

    Excellent,that was the idea,to get it,without too much help... :smile: Anyways,i was asleep... :tongue2:


    P.S.I didn't dream of your exercise... :tongue2:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook