1. Not finding help here? Sign up for a free 30min 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!

Electric energy - potential difference problem!

  1. May 22, 2009 #1
    1. The problem statement, all variables and given/known data

    On planet Tehar, the free-fall acceleration is the same as that on Earth, but there is also a strong downward electric field that is uniform close to the planet's surface. A 2.00 kg ball having a charge of 5.00 µC is thrown upward at a speed of 20.1 m/s. It hits the ground after an interval of 4.10 s. What is the potential difference between the starting point and the top point of the trajectory?


    2. Relevant equations

    Work = (q)(E)(delta x)

    q=charge, E= electric field

    delta V = (delta PE)/q

    V=electric potential difference

    3. The attempt at a solution

    I pretty sure we'd have to use the conservation of energy to determine the solution and the a physics 1 kinematic equation. I know the background of the question but I just can't figure out how the electric field comes into play for the question. Can someone please help me understand this question? Thanks a lot in advance for your help.
     
  2. jcsd
  3. May 23, 2009 #2

    LowlyPion

    User Avatar
    Homework Helper

    Remember at all times on Tehar F = MA.

    Determine through regular kinematics what the acceleration is on the ball.

    F = m*g + q*E = m*a

    So ...

    q*E = m*a - m*g = m*(a - g)

    This suggests that the E field (which is uniform) is

    E = m*(a - g) / q

    Whether the field is ± is determined by whether the Electrostatic force is attracting or repelling.
     
  4. May 23, 2009 #3
    Got the correct answer! Thanks a lot.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Electric energy - potential difference problem!
  1. Electrical energy (Replies: 6)

Loading...