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Good Question?

  1. Aug 6, 2003 #1
    A plastic pellet has a mass of 7.5 X 10^-10 kg and carries a charge of 2.00 X 10^-9 C. The pellet is fired horizontally betweenm a pair of oppositely charged parallel plates. If the electric field strength between the plates is 9.20 X 10^4 N/C and the pellet enters with an initial speed of 150 m/s, determine the deflection angle.

    This is the diagram

    + + + + + + + + + + + + + + +

    Q+ -------------------------------
    \deflection angle(not sccurate drawing)
    - - - - - - - - - - - ------ - - -
    | <-- 2.0cm ----------------->|

    *I am almost positive that this problem can be solved by taking the arctan of the change in X over the change in y but i am not sure how to get there. Not in this sense anyway. I can solve these sort of problems when they are not part of electricity.
    Last edited by a moderator: Aug 6, 2003
  2. jcsd
  3. Aug 6, 2003 #2
    You know that by entering the electric field, the pellet will experience a force. If I understood the problem correctly the force will be perpendicular to the travel direction of the pellet.

    The time spent btw the capacitor can be found; distance/velocity = 2 cm/150

    The force can be found since E=F/q

    Solve for the force.


    solve for acceleration

    you know the amount of time it has accelerated as well as the value of the acceleration, therefore solve for the distance that the pellet has traveled in the verticle direction.

    Now make a triangle. Verticle value being the value above, horizontal value being 2 cm. Find the angle of this triangle and there you go.
  4. Aug 10, 2003 #3
    The pellet follows a parabola, not a straight line so you must get the arctan of vy over vx.
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