Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Motion question

  1. May 23, 2005 #1


    User Avatar

    An electron has a mass of 9.1*10^-31 kg. Between the electrodes of a cathode-ray tube, it moves a distance of 4.0mm, accelerated by a net electrical force of 5.6*10^-15 N. Assuming it started by rest, find it's acceleration and final velocity.

    I found the acceleration to be 6.15*10^15 m/s^2, which is confirmed by the answer book, but how can I get the final velocity without change in time? distance dont help at all if I dont know average velocity...
  2. jcsd
  3. May 23, 2005 #2


    User Avatar

    u have accel, v1, and distance
    use (v2)^2= (v1)^2 + 2ad
  4. May 23, 2005 #3


    User Avatar
    Science Advisor
    Homework Helper

    Force times distance in the direction of the force is work, and that equals change in kinetic energy.

    OOPs.. two suggestions flying at the same time. They both lead to the same conclusion.
  5. May 24, 2005 #4


    User Avatar

    Ok I see, thanks.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook