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Electric Potential slowing a charged particle to a stop

  1. Mar 17, 2019 at 7:09 AM #1
    1. The problem statement, all variables and given/known data
    A particle (mass 6.7 × 10–27 kg, charge 3.2 × 10–19 μC) moves along the positive x axis with
    a speed of 4.8 × 105 m/s. It enters a region of uniform electric field parallel to its motion
    and comes to rest after moving 2.0 m into the field. What is the magnitude of the electric
    a) 2.5 KN/C
    b) 1.5 KN/C
    c) 1.2 KN/C
    d) 3.5 KN/C
    e) 2.4 KN/C

    2. Relevant equations
    (delta)E.E = -q * (E.d)

    3. The attempt at a solution
    (1/2*(6.7*10^-27)*(4.8*10^5)^2)/( (3.2*10^-19) * 10^-6) *2)

    The problem is that when I convert the charge from uc to c I get the answer but multiplied by a number like million and when I divide it by 1000 to get KN still the number remains multiplied by a factor of 1/10. On the other hand, if I leave the charge in uc I get the answer when I divide by 1000 as I should. I feel that I messed a step in the middle or there is a mistake in the question
    Thanks in advance
    Last edited by a moderator: Mar 18, 2019 at 9:54 AM
  2. jcsd
  3. Mar 17, 2019 at 7:27 AM #2


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    The smallest mass a particle (electron or proton) can have is 1.6 *10-19C. An ionized particle can have a multiple of it. So the μC should be a mistake.
  4. Mar 17, 2019 at 8:34 AM #3
    yes, it turned out that the question is written incorrectly; (uc) should be (c) in this question.
    Thank you so much
  5. Mar 17, 2019 at 9:40 PM #4
    Think about the kinematic equations. What's the acceleration? Then use ##F=ma##
  6. Mar 17, 2019 at 11:00 PM #5


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    That was not the issue. See posts 2 and 3.
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