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Motion question

  1. May 23, 2005 #1


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    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


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


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    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


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    Ok I see, thanks.
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